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

glaciations of the west coast range tasmania geomorphic stratigraphic palynologic and 14c evidence indicates that the west coast range tasmania was glaciated at least three times during the late cenozoic the last or margaret glaciation commenced after 30 000 yr b p culminated about 19 000 yr b p and ended by 10 000 yr b p during this period a small ice cap ca 250 m thick and cirque and valley glaciers covered 108 km2 the glacial deposits show little chemical weathering or erosional dissection the snow line ranged from 690 to 1000 m with an average of 830 m for the ice cap mean temperature was 6 5 c below the present temperature during the preceding henty glaciation a 300 to 400 m thick ice cap and outlet glaciers exceeded 1000 km2 the glacial deposits are beyond 14c assay they are more weathered chemically and more dissected than margaret age deposits and the degree suggests a pre last interglaciation age 130 000 yr b p the snow line of the ice cap lay at 740 m and annual temperature was reduced by 7 c ice of the earliest linda glaciation slightly exceeded that of the henty glaciation but had a similar distribution the glacial deposits are intensely weathered have reversed magnetization and overlie a paleosol containing pollen of tertiary type an early pleistocene or tertiary age is indicated

late pleistocene glaciation of the kosciuszko massif snowy mountains australia abstract late pleistocene glaciation of the australian mainland was restricted to a small area of the southeastern highlands geomorphic mapping of the area and exposure dating using the in situ produced cosmogenic isotope 10be provides evidence for at least two distinct glaciations the early kosciuszko glaciation consisted of a single glacier advance before 59 300 5400 years ago snowy river advance the late kosciuszko glaciation comprised three glacier advances 32 000 2500 headley tarn advance 19 100 1600 blue lake advance and 16 800 1400 years ago mt twynam advance the early kosciuszko glaciation was the most extensive and the late kosciuszko advances were progressively less extensive these periods of glaciation in the highlands correspond to episodes of periglacial activity and peaks in lake levels and river discharge at lower elevations in southeastern australia glacier advances on the kosciuszko massif correlate with advances in tasmania south america and new zealand and are broadly representative of hemispheric climate changes during the last glacial cycle

cosmogenic chlorine 36 from calcium spallation calcium is a major target element for cosmogenic 36cl production consequently 36cl rapidly reaches detectable levels in minerals such as calcite and calcium feldspar exposed at the earth s surface spallation of calcium isotopes typically accounts for 80 90 of 36cl production in these minerals with subsidiary contributions from negative muon capture by 40ca and thermal neutron capture by 35cl to provide a basis for surface exposure dating we have calibrated cosmogenic 36cl production in calcium feldspar from the 17 300 year old tabernacle hill basalt at an altitude of 1445 m and an effective geomagnetic latitude of 40 9 the calcium spallation rate is 152 11 atoms g ca 1 a 1 the corresponding rate at sea level and high latitude is estimated at 48 8 3 4 atoms g ca 1 a 1 the muon capture rate used to derive these values is 8 8 2 2 atoms g ca 1 a 1 at the tabernacle hill site scaled from a value of 4 8 1 2 atoms g ca 1 a 1 at sea level and high latitude the calcium spallation rate determined in this study is in excellent agreement with previous whole rock calibration measurements at tabernacle hill when these are recalculated with respect to the absolute timescale the calibration of 36c1 production from calcium underpins development of an exposure dating technique for calcite due to its high calcium content the 36cl production rate in calcite is higher than in any other common rock forming mineral measurement of 36cl in calcite with an accelerator mass spectrometric detection limit of 5 103 atoms per gram allows dating of limestone surfaces exposed for periods ranging from 102 106 years alternatively erosion rates from less than 1 to greater than 1000 m per year can be determined in the case of eroding karst surfaces though the 36cl production rate is lower in calcium feldspar than in calcite measurements on this mineral will provide a useful means of dating young basalt lavas

seismic moment catalog of large shallow earthquakes 1900 to 1989 we compile a worldwide catalog of shallow depth 70 km and large ms 7 earthquakes recorded between 1900 and 1989 the catalog is shown to be complete and uniform at the 20 sec surface wave magnitude ms 7 0 we base our catalog on those of abe 1981 1984 and abe and noguchi 1983a b for events with ms 7 0 those catalogs however are not homogeneous in seismicity rates for the entire 90 year period we assume that global rates of seismicity are constant on a time scale of decades and most inhomogeneities arise from changes in instrumentation and or reporting we correct the magnitudes to produce a homogeneous catalog the catalog is accompanied by a reference list for all the events with seismic moment determined at periods longer than 20 sec using these seismic moments for great and giant earthquakes and a moment magnitude relationship for smaller events we produce a seismic moment catalog for large earthquakes from 1900 to 1989 the catalog is used to study the distribution of moment released worldwide although we assumed a constant rate of seismicity on a global basis the rate of moment release has not been constant for the 90 year period because the latter is dominated by the few largest earthquakes we find that the seismic moment released at subduction zones during this century constitutes 90 of all the moment released by large shallow earthquakes on a global basis the seismic moment released in the largest event that occurred during this century the 1960 southern chile earthquake represents about 30 to 45 of the total moment released from 1900 through 1989 a frequency size distribution of earthquakes with seismic moment yields an average slope b value that changes from 1 04 for magnitudes between 7 0 and 7 5 to b 1 51 for magnitudes between 7 6 and 8 0 this change in the b value is attributed to different scaling relationships between bounded large and unbounded small earthquakes thus the earthquake process does have a characteristic length scale that is set by the downdip width over which rupture in earthquakes can occur that width is typically greater for thrust events at subduction zones than for earthquakes along transform faults and other tectonic environments

rapid flooding of the sunda shelf a late glacial sea level record the increase in sea level from the last glacial maximum has been derived from a siliciclastic system on the tectonically stable sunda shelf in southeast asia the time from 21 to 14 thousand calendar years before the present has been poorly covered in other records the record generally confirms sea level reconstructions from coral reefs the rise of sea level during meltwater pulse 1a was as much as 16 meters within 300 years 14 6 to 14 3 thousand years ago

late cainozoic glaciation in western tasmania australia abstract four major quaternary glaciations with associated interglaciations and interstadials have been identified in tasmania for which some chronological cotrol is given by radiocarbon and amino acid assays pollen analysis and relative weathering characteristics the glaciations are known as the margaret henty moore and linda the margaret glaciations has two clear stadial intervals isotope stages 4 and 2 separated by the tullabardine interstadial dated at ca 50 25 ka bp an interglaciation corresponding to isotope stage 5 pieman interglaciation is characterised by sediments containing a pollen assemblage of a temperate rain forest weathered glacial deposits lying beneath the pieman sediments are inferred to be those of the penultimate glaciation three stadial moraines are identified a preceding interglaciation langdon contains wood that yielded an amino acid ratio equivalent to the age of marine isotope stage 7 the following moore glaciation had three stadial intervals two of which are separated by a clear interstadial baxter with organic sediments that have amino acid ages equivalent to isotope stage 10 the non glacial sediments have a drm of normal polarity and are inferred to be of mid quaternary age the oldest interglaciation regency is identified from organic rich sediments pollen assemblage of a temperate rain forest overlying intensely weathered glacial deposits that have a drm with reversed polarity i e 730 ka the linda glaciation is the most extensive of all in tasmania although dating is uncertain it has been assigned tentatively to the early quaternary

probabilistic forecasting of earthquakes we present long term and short term forecasts for magnitude 5 8 and larger earthquakes we discuss a method for optimizing both procedures and testing their forecasting effectiveness using the likelihood function our forecasts are expressed as the rate density that is the probability per unit area and time anywhere on the earth our forecasts are for scientific testing only they are not to be construed as earthquake predictions or warnings and they carry no official endorsement for our long term forecast we assume that the rate density is proportional to a smoothed version of past seismicity using the harvard cmt catalogue this is in some ways antithetical to the seismic gap model which assumes that recent earthquakes deter future ones the estimated rate density depends linearly on the magnitude of past earthquakes and approximately on a negative power of the epicentral distance out to a few hundred kilometres we assume no explicit time dependence although the estimated rate density will vary slightly from day to day as earthquakes enter the catalogue the forecast applies to the ensemble of earthquakes during the test period it is not meant to predict any single earthquake and no single earthquake or lack of one is adequate to evaluate such a hypothesis we assume that 1 per cent of all earthquakes are surprises assumed uniformly likely to occur in those areas with no earthquakes since 1977 we have made specific forecasts for the calendar year 1999 for the northwest pacific and southwest pacific regions and we plan to expand the forecast to the whole earth we test the forecast against the earthquake catalogue using a likelihood test and present the results our short term forecast updated daily makes explicit use of statistical models describing earthquake clustering like the long term forecast the short term version is expressed as a rate density in location magnitude and time however the short term forecasts will change significantly from day to day in response to recent earthquakes the forecast applies to main shocks aftershocks aftershocks of aftershocks and main shocks preceded by foreshocks however there is no need to label each event and the method is completely automatic according to the model nearly 10 per cent of moderately sized earthquakes will be followed by larger ones within a few weeks

exposure dating and validation of periglacial weathering limits northwest scotland periglacial weathering limits on two mountains in northwest scotland separate zones of contrasting exposure history exposure dating of bedrock below the weathering limits gives ages consistent with late devensian deglaciation but six out of seven samples from above the weathering limits give minimum exposure ages older than late devensian ice expansion these results suggest that mountain summits stood as nunataks above the last ice sheet surface and rule out formation of weathering limits by periglacial rock breakdown since deglaciation trimming of frost debris during an ice sheet readvance or enhanced weathering prior to climatic warming during ice sheet downwastage the dating results do not preclude the possibility that weathering limits mark a former englacial boundary between passive cold based ice on mountain summits and erosive warm based ice at lower elevations although 26 al 10 be ratios for high level bedrock surfaces provide no evidence of prolonged static ice cover

novel 3d sequence stratigraphic numerical model for syn rift basins analysing architectural responses to eustasy sedimentation and tectonics syn rift clastic sedimentary systems preserve a complicated stratigraphic architecture that records the interplay of tectonics eustatic sea level and storage and routing of sediments previous conceptual models describe and explain changes in depositional stacking patterns along a fault segment however stacking patterns and the nature of key stratigraphic surfaces is challenging to predict accurately with conventional sequence stratigraphic models that do not consider the three dimensional interplay of subsidence sedimentation and eustasy we present a novel geometric 3d sequence stratigraphic model syn strat which applies temporally and spatially variable fault scale tectonic constraints to stratigraphic forward modelling as well as allowing flexibility in the other controls in time and space syn strat generates a 3d graphical surface that represents accommodation although the model has the capacity to model footwall variation here we present model results from the hangingwall of a normal fault with temporal and spatial dip and strike predictions made of stacking patterns and systems tracts for a given set of controls sensitivity tests are tied to the depositional architecture of field based examples from the loreto basin gulf of california and alkyonides basin gulf of corinth here the relative influence of major sedimentary controls different subsidence histories varying sedimentation distribution including along strike variation in stacking patterns are assessed and demonstrate the potential of syn strat for reducing subsurface uncertainties by resolving multiple scenarios in addition the model demonstrates the nature of diachroneity of key stratigraphic surfaces that can arise in syn rift settings which could be represented by a bypass surface sequence boundary or reservoir seal maximum flooding surface in the rock record enabling a quantitative assessment of these surfaces is critical for prospect analysis in hangingwall half graben fills where these surfaces are heavily relied upon for well correlations that are used for hydrocarbon volume and production rate predictions

cosmogenic 36cl accumulation in unstable landforms 1 effects of the thermal neutron distribution cosmogenic nuclides produced in situ within minerals at the surface of the earth are proving to be an effective means of assessing geomorphic histories the use of multiple cosmogenic nuclides permits both exposure times and erosion rates to be determined however if two nuclides are produced only by spallation reactions the systematic differences in their accumulation rates depend only on the differences in their production rates and half lives the relatively small differences that result require a high degree of analytical precision to yield useful results in contrast to other spallogenic nuclides sup 36 cl is also produced by low energy neutron absorption which creates a different pattern of production as a function of depth we have measured the thermal flux with depth in a concrete block using sup 3 he filled neutron detectors the measured thermal neutron profile agrees well with predictions from a simple diffusion based thermal neutron distribution model calculations of sup 36 cl production using the model suggest that the use of sup 36 cl along with a purely spallogenic nuclide to determine erosion rates and exposure times should be less sensitive to analytical error than are determinations from two purely spallogenic nuclides 31 refs 7 figs 3 tabs

towards a climate event stratigraphy for new zealand over the past 30 000 years nz intimate project it is widely recognised that the acquisition of high resolution palaeoclimate records from southern mid latitude sites is essential for establishing a coherent picture of inter hemispheric climate change and for better understanding of the role of antarctic climate dynamics in the global climate system new zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the southern hemisphere westerly circulation zone a critical transition zone between subtropical and antarctic influences new zealand has mountainous axial ranges that amplify the climate signals and consequently the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions since 1995 intimate has through a series of international workshops sought ways to improve procedures for establishing the precise ages of climate events and to correlate them with high precision for the last 30 000 calendar years the nz intimate project commenced in late 2003 and has involved virtually the entire new zealand palaeoclimate community its aim is to develop an event stratigraphy for the new zealand region over the past 30 000 years and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from northern hemisphere records e g last glacial maximum lgm termination i younger dryas an initial outcome of nz intimate has been the identification of a series of well dated high resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal yr bp to the present day high resolution records for the last glacial coldest period lgcp including the lgm sensu stricto and last glacial interglacial transition lgit from auckland maars kaipo and otamangakau wetlands on eastern and central north island marine core md97 2121 east of southern north island speleothems on northwest south island okarito wetland on southwestern south island are presented discontinuous fragmentary records comprising compilations of glacial sequences fluvial sequences loess accumulation and aeolian quartz accumulation in an andesitic terrain are described comparisons with ice core records from antarctica epica dome c and greenland gisp2 are discussed a major advantage immediately evident from these records apart from the speleothem record is that they are linked precisely by one or more tephra layers based on these new zealand terrestrial and marine records a reasonably coherent regionally applicable sequence of climatically linked stratigraphic events over the past 30 000 cal yr is emerging three major climate events are recognised 1 lgcp beginning at ca 28 000 cal yr bp ending at termination i ca 18 000 cal yr bp and including a warmer and more variable phase between ca 27 000 and 21 000 cal yr bp 2 lgit between ca 18 000 and 11 600 cal yr bp including a lateglacial warm period from ca 14 800 to 13 500 cal yr bp and a lateglacial climate reversal between ca 13 500 and 11 600 cal yr bp and 3 holocene interglacial conditions with two phases of greatest warmth between ca 11 600 and 10 800 cal yr bp and from ca 6 800 to 6 500 cal yr bp some key boundaries coincide with volcanic tephras copyright 2007 john wiley sons ltd

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

challenges for a cross disciplinary geoarchaeology the intersection between environmental history and geomorphology abstract geoarchaeology is a growing subfield of cross disciplinary research at the intersection between geomorphology environmental history and archaeology this prospective essay does not aim to analyze the nature or evolution of geoarachaeology or to review available techniques and methods instead it addresses challenges exciting challenges confront geoarchaeology in the form of persistent problems that demand satisfactory solutions despite improving skills and innovative technologies drawing from the full record of human history a number of practical issues can be highlighted to explicate these challenges 1 open air archaeological sites are the main object of study for the early to mid pleistocene even though they represent open systems that raise fundamental questions about archaeo taphonomic integrity how were sites buried and then modified by selective preservation horizontal or vertical disturbance and the role of carnivores is it possible to determine the degree to which such sites accurately record prehistoric human behavior prior to the late pleistocene when hearths and living structures lend better definition to occupation surfaces can non primary open air sites also shed light on human activities and environmental history 2 cave sites have long been favored by archaeologists because of the impression that they represent relatively complete and undisturbed archaeostratigraphic sequences but serious problems also exist here in regard to the nature of accumulation and the sources of mineral and biogenic sediments in what were open systems liable to disturbance despite comparatively low energy processes 3 less familiar are urban and other architectural sites where processes of formation and degradation mimic natural sedimentation and erosion such a geoarchaeology can be highly informative for urban processes demographic cycles or the intersection between sites and their surrounding landscapes 4 spatial components of geoarchaeological research need more systematic consideration for locational strategies and with an appreciation that site presence or absence allows a more dynamic modeling of settlement and procurement strategies 5 regional settlement expansion and contraction may also inform on mosaic evolution or pleistocene dispersals including the out of africa hypothesis 5 finally multiple themes connected with environmental degradation during holocene times may open new windows to examine specific problems by objective criteria so contributing to a wider academic discourse about long term trends the interfingering of climatic and land use factors in cause and effect dilemmas or the construction of future scenarios in an era of accelerating planetary change the focus of archaeology is shifting to later ranges of prehistory so that geoarchaeologists now have a mandate to engage more directly with urban spatial and degradation issues this should be met with a broader and more inclusive agenda one that optimizes on expertise with historical geomorphology and environmental history but in collaboration with archaeologists and other social scientists that would sustain a more prominent role for geoarchaeology in the university curriculum

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

sea surface temperatures of the southwest pacific ocean during the last glacial maximum the southwest pacific ocean covers a broad range of surface water conditions ranging from warm salty water in the subtropical east australian current to fresher cold water in the circumpolar current using a new database of planktonic foraminifera assemblages ausmat f2 we demonstrate that the modern analog technique can be used to accurately reconstruct the magnitude of sea surfacetemperature sst in this region we apply this technique to data from 29 deep sea cores along a meridional transect of the southwest pacific ocean to estimate the magnitude of sst cooling during the last glacial maximum we find minimal cooling in the tropics 0 2 c moderate cooling in the subtropical midlatitudes 2 6 c and maximum cooling to the southeast of new zealand 6 10 c the magnitude of cooling at the sea surface from the tropics to the temperate latitudes is found to generally be less than cooling at the surface of adjacent land masses

improving in situ cosmogenic chronometers new radiocarbon ages for sierra nevada deglaciation the first 10 be measurements from the laurentide terminal moraine and calculations based on paleomagnetic field strength have the potential to substantially improve the accuracy of cosmogenic age estimates specifically three new constraints apply to the interpretation of measured abundances of in situ produced cosmogenic 10be and 26al 1 a suite of minimum limiting radiocarbon dates indicates that the sierra nevada was deglaciated at least several thousand years earlier than assumed when nishiizumi et al 1989 first calibrated 10be and 26 al production rates based on polished bedrock surfaces in the range with retreat beginning by 18 000 cal yr b p and completed by 13 000 cal yr b p 2 concentrations of 10be in moraine boulders and glacier polished bedrock in new jersey show little variance 10 1 and can be used to calculate a preliminary 10be production rate integrated over the past 21 000 22 000 cal yr b p at 41 200 300 m altitude that is about 20 lower than currently accepted 3 calculations of the effect of past geomagnetic field strength variations on production rates suggest that the use of temporally averaged production rates may generate age errors of 20 however cosmogenic exposure ages can be corrected for this effect although the corrections currently are imprecise many previously reported late pleistocene 10be and 26al exposure ages are probably too young and are less accurate and less precise than implied by reported uncertainties the discrepancy between accepted production rates and those calculated from laurentide exposures when considered together with the sierran deglacial chronology and the model results suggest that correlations between cosmogenic and other numerical ages especially for brief events like the younger dryas and heinrich events will not be robust until temporal variations and the altitude latitude scaling of production rates are fully understood and quantified at levels comparable to current analytic uncertainties 3

chronology for fluctuations in late pleistocene sierra nevada glaciers and lakes mountain glaciers because of their small size are usually close to equilibrium with the local climate and thus should provide a test of whether temperature oscillations in greenland late in the last glacial period are part of global scale climate variability or are restricted to the north atlantic region correlation of cosmogenic chlorine 36 dates on sierra nevada moraines with a continuous radiocarbon dated sediment record from nearby owens lake shows that sierra nevada glacial advances were associated with heinrich events 5 3 2 and 1

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

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

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

the timing of the last glacial maximum in australia abstract late pleistocene glaciation of australia was restricted to the snowy mountains and the tasmanian highlands glaciers were most extensive in tasmania where ice caps formed on the central plateau and west coast ranges and systems of valley and cirque glaciers formed on surrounding mountains to investigate the timing of maximum glacier advance during the last glacial maximum lgm we dated boulders on 18 moraines in 8 glaciated areas using cosmogenic 36cl and 10be we sampled moraines deposited by cirque and valley glaciers in a range of climate types and lithologies over a 7 latitudinal and a 1430 m altitudinal transect exposure ages for lgm moraine boulders group tightly in the range 17 20 ka boulders from the hamilton moraine often treated as the lgm type moraine range in age from 190 350 ka indicating that it was deposited well before the last glaciation collectively the exposure ages show that southeastern australia was glaciated briefly during and after the lgm and deglaciated well before the holocene ice retreated from the terminal moraines after the period of coldest sea surface temperatures in the southwest pacific ocean no evidence was found for readvance of glaciers during the antarctic cold reversal or the younger dryas period

statistical analysis of the central europe seismicity abstract the aim of this paper is to characterize the spatio temporal distribution of central europe seismicity specifically by using a non parametric statistical approach the proportional hazard model leading to an empirical estimation of the hazard function we provide some constrains on the time behavior of earthquake generation mechanisms the results indicate that the most conspicuous characteristics of mw 4 0 earthquakes is a temporal clustering lasting a couple of years this suggests that the probability of occurrence increases immediately after a previous event after a few years the process becomes almost time independent furthermore we investigate the cluster properties of the seismicity of central europe by comparing the obtained result with the one of synthetic catalogs generated by the epidemic type aftershock sequences etas model which previously have been successfully applied for short term clustering our results indicate that the etas is not well suited to describe the seismicity as a whole while it is able to capture the features of the short term behaviour remarkably similar results have been previously found for italy using a higher magnitude threshold

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

the velocity description of deformation paper 1 theory abstract there are several advantages in using velocities to describe the deformation of the crust and lithosphere induced by extension compression isostasy and other processes 1 the method is very general any deformation style can be described in this way simple examples are pure shear inclined or vertical simple shear bulk rotation airy or flexural isostasy and compaction 2 velocity fields can be combined to model more complex deformation 3 the syn tectonic evolution of parameters such as temperature pressure hydrocarbon maturity and porosity are easily modelled once the deformation velocities are specified 4 the syn tectonic evolution of sedimentary architectures can be modelled using a general tectono sedimentary forward modelling equation which incorporates the deformation velocities these advantages are illustrated by a computer model which simulates clastic sediments prograding into an active half graben formed by extension above a listric fault processes included in this model are compaction of the sediments hanging wall deformation by inclined simple shear and simultaneous footwall deformation to avoid space problems the velocity field for the hanging wall block above the non rigid footwall must obey a simple contact condition

the timing of linear dune activity in the strzelecki and tirari deserts australia abstract linear dunes occupy more than one third of the australian continent but the timing of their formation is poorly understood in this study we collected 82 samples from 26 sites across the strzelecki and tirari deserts in the driest part of central australia to provide an optically stimulated luminescence chronology for these dunefields the dunes preserve up to four stratigraphic horizons bounded by palaeosols which represent evidence for multiple periods of reactivation punctuated by episodes of increased environmental stability dune activity took place in episodes around 73 66 35 32 22 18 and 14 10 ka intermittent partial mobilisation persisted at other times throughout the last 75 ka and dune activity appears to have intensified during the late holocene dune construction occurred when sediment was available for aeolian transport in the strzelecki and tirari deserts this coincided with cold arid conditions during marine isotope stage mis 4 late mis 3 and mis 2 and the warm dry climates of the late pleistocene holocene transition period and late holocene localised influxes of sediment on active floodplains and lake floors during the relatively more humid periods of mis 5 also resulted in dune formation the timing of widespread dune reactivation coincided with glaciation in southeastern australia along with cooler temperatures in the adjacent oceans and antarctica

using palaeoenvironmental dna to reconstruct past environments progress and prospects palaeoenvironmental dna palendna is defined as ancient dna adna originating from disseminated genetic material within palaeoenvironmental samples sources of palendna include marine and lake sediments peat loess till ice permafrost palaeosols coprolites preserved gut contents dental calculus tephras and soils as well as deposits in caves rockshelters and at archaeological sites palendna analysis provides a relatively new tool for quaternary and archaeological sciences and its applications have included palaeoenvironmental and palaeodietary reconstructions testing hypotheses regarding megafaunal extinctions human environment interactions taxonomic studies and studies of dna damage because palendna samples comprise markedly different materials and represent wide ranging depositional and taphonomic contexts various issues must be addressed to achieve robust reproducible findings such issues include climatic and temporal limitations the biological origin and state free versus bound of palendna stratigraphic reliability sterile sampling ability to distinguish modern from adna signals dna damage and pcr amplification dna extraction methods and taxonomic resolution in this review we provide a non specialist introduction to the use of palendna for quaternary and archaeological researchers assess attributes and limitations of this palaeoenvir onmental tool and discuss future prospects of using palendna to reconstruct past environments copyright 2014 the authors journal of quaternary science published by john wiley sons ltd on behalf of quaternary research association

palynological analysis of the late early pleistocene sediments from queque cave in guangxi south china abstract palynomorphs extracted from the sediments in queque cave of the late early pleistocene in chongzuo guangxi zhuang autonomous region were investigated to reconstruct the paleoenvironment in the study area while the sediments are pollen poor they are sufficiently productive to carry out a paleoenvironmental analysis the source vegetation reflected by the palynomorphs from the unfossiliferous layer was temperate to warm temperate deciduous and evergreen broadleaved forest while it was warm temperate to subtropical deciduous and evergreen broadleaved forest from the mammalian horizons climatic parameters obtained using the coexistence approach indicate that the unfossiliferous layer mat 11 3 15 4 c map 601 1 1076 1 mm was cooler and drier than that from the mammal bearing layers mat 12 6 18 6 c map 784 7 1523 1 mm

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

the factors related to the occurrence rate of m 4 earthquakes near japanese onshore faults abstract this study investigates which geological and seismicity covariates are most related to the hazard rate along active faults within mainland japan the hazard rate is defined to be the rate of m 4 earthquakes occurring around the fault to investigate the relationship between the hazard rate and the covariates we use cox proportional hazards models each model makes use of all available data by including repeat events large earthquakes that have occurred along the same fault and adjusts for the correlation resulting from the recurrent nature of the data all models show that the recent seismicity rate and length of the fault significantly increase the hazard rate of m 4 earthquakes furthermore we illustrate how the estimated model can be extended to potentially forecast other periods of interest

late quaternary erosion events in lowland and mid altitude tasmania in relation to climate change and first human arrival abstract the establishment of a chronology of landscape forming events in lowland and mid altitude tasmania essential for assessing the relative importance of climatic and human influences on erosion and for assessing present erosion risk has been limited by the small number of ages obtained and limitations of dating methods in this paper we critically assess previous tasmanian studies list published radiocarbon ages considered to be dependable present new radiocarbon and thermoluminescence tl ages for 25 sites around tasmania and consider the evidence for the hypotheses that erosion processes at low and mid altitudes have been 1 purely climatically controlled and 2 influenced both by climatic and anthropogenic increased fire frequency effects a total of 94 dependable finite ages calibrated for radiocarbon and as measured for tl and optically stimulated luminescence osl determinations are listed for deposits comprising dunes colluvium alluvium and loess like aeolian deposits two fall in the 100 ka period 15 fall in the period 65 35 ka and 77 fall in the period 35 0 3 ka there was a sustained increase in erosion recorded in the period 35 15 ka as reflected by a greater number of dated aeolian deposits during this period we considered three possible biases that may have affected the age distribution obtained the limitations of radiocarbon dating sampling bias and preservation bias sampling bias may have favoured more recent dune strata but radiocarbon dating and preservation biases are unlikely to have significantly distorted the age distribution obtained long but intermittent aeolian deposition is recorded at two sites southwood b c 59 28 ka and dunlin dune c 29 14 ka but there is no evidence of regional loess deposits such as found in new zealand the timing of increased erosion in tasmania between 35 and 30 ka approximately coincides with the intermittent ten fold increase of dust accumulation between 33 and 30 ka in the antarctic dome c ice core the absence of widespread erosion before 35 ka the abrupt increase of erosion around this time the frequent association of erosion products with charcoal the arrival of people in tasmania at c 40 cal ka and the known use of fires by aborigines to maintain areas of non climax vegetation suggest that ecosystem disturbance by anthropogenic fires in a drier climate than that presently prevailing may have contributed to erosion in lowland and mid altitude tasmania after 35 ka thus the tasmanian erosion record provides circumstantial support for the proposition that human dispersal in southeast australia was accompanied by significant ecological change

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

sea level at the last glacial maximum evidence from northwestern australia to constrain ice volumes for oxygen isotope stage 2 new sea level information from the bonaparte gulf in northwestern australia is used to constrain the magnitude and rates of change of ice volumes during the last glacial maximum lgm the region is tectonically stable and far from the former ice covered regions the glacio hydro isostatic adjustment of the coast is therefore relatively small and the corrections for this evect are not sensitive to details of the rebound model microfossil analysis and ams radiocarbon dating of 11 gravity cores taken across the shelf and bonaparte gulf demonstrate that 1 the lgm sea levels were locally at 125 4 m 2 the lgm terminated abruptly at 19 000 cal yr bp with a rapid rise in sea level of about 15 m over the next 500 years and 3 the onset of the minimum sea levels occurred before 22 000 cal yr bp when corrected for the glacio hydro isostatic evects the increase of lgm ice volumes over the present day ice volume is 52 5 106 km3 the termination of the lgm is marked by a rapid ice discharge of 5 2 106 km3 2001 elsevier science b v all rights reserved

variations in earthquake size distribution across different stress regimes the earthquake size distribution follows in most instances a power law1 2 with the slope of this power law the b value commonly used to describe the relative occurrence of large and small events a high b value indicates a larger proportion of small earthquakes and vice versa statistically significant variations of b values have been measured in laboratory experiments mines and various tectonic regimes such as subducting slabs near magma chambers along fault zones and in aftershock zones3 however it has remained uncertain whether these differences are due to differing stress regimes as it was questionable that samples in small volumes such as in laboratory specimens mines and the shallow earth s crust are representative of earthquakes in general given the lack of physical understanding of these differences the observation that b values approach the constant 1 if large volumes are sampled4 was interpreted to indicate that b 1 is a universal constant for earthquakes in general5 here we show that the b value varies systematically for different styles of faulting we find that normal faulting events have the highest b values thrust events the lowest and strike slip events intermediate values given that thrust faults tend to be under higher stress than normal faults we infer that the b value acts as a stress meter that depends inversely on differential stress

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

denudation vertical crustal movements and sedimentary basin infill denudation and vertical crustal movements are linked through the isostatic equation for conservation of lithospheric mass recent empirical results from a wide range of sources are presented on the rates of these processes denudation alone can cause non tectonic isostatic surface uplift of the right magnitude predicted by theory a case is made following ahnert for a single linear relationship although with much scatter between denudation rate and mean drainage basin relief for large basins some recent determinations of denudational time constants have neglected to include tectonic and isostatic terms which oppose the reduction of relief by denudation application of diffusional transport models to determine the rate of sediment deposition are severely limited by inherent one dimensionality and neglect of suspended and washload contributions basin infill sequences may be used to determine past sediment transfer coefficients from a hinterland but problems arise in the apportionment of the various hinterland fluxes that occur in real world three dimensional basins sediment yields in smaller half graben and growth fold basins must reflect the magnitude of drainage basins and the complex local controls upon sediment yields examples are given from extensional basins in the western usa and greece the length of tectonic relief produced in tilt blocks and growth folds will control the area of drainage basin developed through the fractal form of hack s law and hence the magnitude of deposition in sedimentary basins adjoining tectonic uplands

significance of stress transfer in time dependent earthquake probability calculations 1 a sudden change in stress is seen to modify earthquake rates but should it also revise earthquake probability data used to derive input parameters permit an array of forecasts so how large a static stress change is required to cause a statistically significant earthquake probability change to answer that question effects of parameter and philosophical choices are examined through all phases of sample calculations drawing at random from distributions of recurrence aperiodicity pairs identifies many that recreate long paleoseismic and historic earthquake catalogs probability density functions built from the recurrence aperiodicity pairs give the range of possible earthquake forecasts under a point process renewal model consequences of choices made in stress transfer calculations such as different slip models fault rake dip and friction are tracked for interactions among large faults calculated peak stress changes may be localized with most of the receiving fault area changed less than the mean thus to avoid overstating probability change on segments stress change values should be drawn from a distribution reflecting the spatial pattern rather than using the segment mean disparity resulting from interaction probability methodology is also examined for a fault with a well understood earthquake history a minimum stress change to stressing rate ratio of 10 1 to 20 1 is required to significantly skew probabilities with 80 85 confidence that ratio must be closer to 50 1 to exceed 90 95 confidence levels thus revision to earthquake probability is achievable when a perturbing event is very close to the fault in question or the tectonic stressing rate is low

on the spatio temporal distribution of m 7 0 worldwide seismicity with a non parametric statistics abstract the aim of this paper is to provide some constrains on the time behavior of earthquake generation mechanism through the usage of a non parametric statistics that leads up to the empirical estimation of the hazard function the results indicate that the most characterizing temporal feature for large m 7 0 worldwide shallow earthquake occurrence is a clustering lasting few years indicating that the probability of earthquake occurrence is higher immediately after the occurrence of an event after that the process becomes almost time independent as in a poisson process remarkably this time clustering is very similar to what previously found for different spatio magnitude windows and it does not seem to depend on the tectonic style of the region this may support the hypothesis of an universal law for earthquake occurrence

a time and magnitude predictable model for generation of shallow earthquakes in the aegean area repeat times of strong shallow mainshocks have been determined by the use of instrumental and historical data for 68 seismogenic sources in the aegean and surrounding area 34 n 43 n 18 e 30 e for 49 of these sources at least two interevent times three mainshocks are available for each source by using the repeat times for these 49 sources the following relation has been determined log t t 0 36m min 0 35m p a wheret t is the repeat time measured in years m p the surface wave magnitude of the preceding mainshock mmin the magnitude of the smallest earthquake considered and a parameter which varies from source to source a multilinear correlation coefficient equal to 0 89 was determined for this relation

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

late glacial and holocene record of vegetation and climate from cynthia bay lake st clair tasmania a late glacial holocene pollen record was obtained from a 3 96 m sediment core taken from lake st clair central tasmania modern vegetation and pollen analyses formed the basis for interpretation of the vegetation and climate history following deglaciation and before ca 18450 yr bp podocarpus lawrencei coniferous heath and astelia plantago wet alpine herbfield became established at lake st clair a distinct poaceae plantago peak occurs between 18450 and 11210 yr bp and a mean annual temperature depression from ca 6 2 c to 3 c below present is inferred for this period the marked reduction in podocarpus and strong increase of poaceae suggests reduced precipitation levels during the period of widespread deglaciation ca 18 5 11 kyr bp the local late pleistocene holocene non forest to forest biostratigraphical boundary is dated at 11 2 kyr bp it is characterised by expansion of the subalpine taxa athrotaxis diselma with nothofagus gunnii and by the establishment of nothofagus cunninghamii with eucalyptus spp a phyllocladus bulge prior to the expansion of nothofagus cunninghamii reported at other tasmanian sites is not present at lake st clair nothofagus cunninghamii cool temperate rainforest peaked at 7800 yr bp probably under wetter climatic conditions than present the maximum development of rainforest in the early middle holocene may indicate that the temperature was slightly warmer than present but the evidence is not definitive the expansion of eucalyptus spp and poaceae after 6000 yr bp may be partly a disclimax effect as a result of aboriginal burning but appears also to reflect reduced precipitation the changes in vegetation and inferred climate can be explained by major changes in synoptic patterns of southern australia and the adjacent southwest pacific copyright 2000 john wiley sons ltd

normal fault control on bedrock channel incision and sediment supply insights from numerical modeling 1 the evolution of footwall drainage basins sediment supply and hanging wall stratigraphy in rift basins is investigated using a coupled numerical model of detachment limited stream network evolution and coarse grained fan delta deposition the response of bedrock channel networks to repeated footwall uplift events leads to increasing sediment supply over tens of thousands of years as the networks initiate and then expand followed by relatively constant sediment supply as the stream networks reach their maximum spatial extent the distinct time lag between the onset of tectonic activity and attainment of maximum sediment supply leads to stratigraphies that are initially aggradational and then progradational much of the variation in sediment supply is the product of the complex response and reorganization of the stream networks to faulting related perturbations and is not directly related to specific faulting events increasing fault displacement drives the system toward a new steady state with a higher sediment supply but is initially expressed as a retrogradation as sediment supply lags behind increased displacement the converse is true for a decrease in fault displacement which is initially expressed as progradation continual stochastic variation in recurrence interval leads to a system that does not achieve a steady state and as a result exhibits continual variation in sediment supply the model results emphasize the local tectonic controls on stratigraphic architectures developed within extensional basins and the complex manner in which stream network growth and response to tectonic activity can be expressed in the stratigraphic record

global seismicity of 2003 centroid moment tensor solutions for 1087 earthquakes abstract centroid moment tensor cmt solutions are presented for 1087 earthquakes that occurred during 2003 the solutions are obtained using the method of dziewonski et al dziewonski a m chou t a woodward j h 1981 determination of earthquake source parameters from waveform data for studies of global and regional seismicity j geophys res 86 2825 2852 and applying corrections for aspherical earth structure as represented by the whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l 1992 acoustic imaging at the planetary scale in emert h harjes h p eds acoustical imaging vol 19 plenum press new york pp 785 797 the model of inelastic attenuation of durek and ekstrom durek j j ekstrom g 1996 a radial model of inelasticity consistent with long period surface wave attenuation bull seism soc am 86 144 158 is used to predict the decay of the waveforms the focal mechanisms of the largest or otherwise significant earthquakes of 2003 are reviewed

long term earthquake clustering summary we analyse statistically the long term properties of several instrumental earthquake catalogues complete catalogues exhibit both short and long term clustering for earthquakes of all depth ranges after accounting for the effect of short term clustering we find that in residual declustered catalogues long term clustering not periodicity characterizes the occurrence of all earthquakes shallow intermediate and deep the degree of clustering in residual catalogues is the same for earthquakes in different depth ranges circumstantial evidence indicates that the long term v ariation of seismicity is governed by a power law temporal distribution as in short term clustering it is scale invariant the fractal dimension of an earthquake set on the time axis is of the order of 0 8 0 9 therefore mainshock occurrence is closer to a stationary poisson process than standard aftershock sequences of shallow earthquakes

how and where do incised valleys form if sea level remains above the shelf edge sequence stratigraphic models predict that during relative sea level fall rivers will cut incised valleys across the exposed continental shelf incision is driven by the exposure of convex up topography and consequent downstream increases in stream power modern shelf profiles from passive margin and foreland basin settings show that profile convexities occur at the shelf edge and at the current highstand coastline the coastal prism in nonglacial times which form much of earth9s history it is unlikely that the shelf edge was subaerially exposed during such periods patterns of incision would have been primarily determined by the shape of the coastal prism on the basis of modern shelf profiles from passive margin and foreland basin settings river incision of as much as 20 to 70 m would be centered upon the preceding highstand coastline and would be restricted to the inner part of the shelf deeper incised valleys would only result from exposure of the shelf edge or from the processes involved in the formation of submarine canyons

beryllium 10 dating of the duration and retreat of the last pinedale glacial sequence accurate terrestrial glacial chronologies are needed for comparison with the marine record to establish the dynamics of global climate change during transitions from glacial to interglacial regimes cosmogenic beryllium 10 measurements in the wind river range indicate that the last glacial maximum marine oxygen isotope stage 2 was achieved there by 21 700 700 beryllium 10 years and lasted 5900 years ages of a sequence of recessional moraines and striated bedrock surfaces show that the initial deglaciation was rapid and that the entire glacial system retreated 33 kilometers to the cirque basin by 12 100 500 beryllium 10 years

evidence of clustering and nonstationarity in the time distribution of large worldwide earthquakes 1 the purpose of this paper is to characterize the statistical distribution of worldwide largest earthquakes we analyze the distribution of worldwide shallow events with ms 7 0 since 1900 by following the occam s razor philosophy we start from the simplest possible model stationary poisson process and we inspect more complicated models only if the data show significant departures from the simplest one the results show two important characteristics first worldwide ms 7 0 earthquakes tend to cluster in time and space with features similar to smaller events second for some seismic regions there is evidence in favor of long term fluctuations of the earthquake rate these results support the hypothesis of universality suggesting that an etas model with a background varying with time can be considered reliable to describe the seismicity distribution over a wide space time magnitude window from a practical point of view our findings suggest that the paradigm that seismic zones are stationary systems implicitly assumed in seismic hazard assessment should be regarded with caution

seismicity based earthquake forecasting techniques ten years of progress abstract earthquake fault systems interact over a broad spectrum of spatial and temporal scales and in recent years studies of the regional seismicity in a variety of regions have produced a number of new techniques for seismicity based earthquake forecasting while a wide variety of physical assumptions and statistical approaches are incorporated into the various methodologies they all endeavor to accurately replicate the statistics and properties of both the historic and instrumental seismic records as a result the last ten years have seen significant progress in the field of intermediate and short term seismicity based earthquake forecasting these include general agreement on the need for prospective testing and successful attempts to standardize both evaluation methods and the appropriate null hypotheses here we differentiate the predominant approaches into models based upon techniques for identifying particular physical processes and those that filter or smooth the seismicity comparison of the methods suggests that while smoothed seismicity models provide improved forecast capability over longer time periods higher probability gain over shorter time periods is achieved with methods that integrate statistical techniques with our knowledge of the physical process such as the epidemic type aftershock sequence etas model or those related to changes in the b value for example in general while both classes of seismicity based forecasts are limited by the relatively short time period available for the instrumental catalog significant advances have been made in our understanding of both the limitations and potential of seismicity based earthquake forecasting there is general agreement that both short term forecasting on the order of days to weeks and longer term forecasting over five to ten year periods is within reach this recent progress serves to illuminate both the critical nature of the different temporal scales intrinsic to the earthquake process and the importance of high quality seismic data for the accurate quantification of time dependent earthquake hazard

earthquake clustering inferred from pliocene gilbert type fan deltas in the loreto basin baja california sur mexico a stacked sequence of pliocene gilbert type fan deltas in the loreto basin was shed from the footwall of the dextral normal loreto fault and deposited at the margin of a marine basin during rapid fault controlled subsidence fan delta parasequences coarsen upward from marine siltstone and sandstone at the base through sandy bottomsets and gravelly foresets to gravelly nonmarine topsets each topset unit is capped by a thin shell bed that records marine flooding of the delta plain several mechanisms may have produced repetitive vertical stacking of gilbert deltas 1 autocyclic delta lobe switching 2 eustatic sea level fluctuations 3 climatically controlled fluctuations in sediment input and 4 episodic subsidence produced by temporal clustering of earthquakes we favor hypothesis 4 for several reasons but hypotheses 2 and 3 cannot be rejected at this time earthquake clustering can readily produce episodic subsidence at spatial and temporal scales consistent with stratigraphic trends observed in the loreto basin this model is supported by comparison with paleoseismological studies that document clustering on active faults over a wide range of time scales earthquake clustering is a new concept in basin analysis that may be helpful for understanding repetitive stratigraphy in tectonically active basins

differentiating the effect of episodic tectonism and eustatic sea level fluctuations in foreland basins filled by alluvial fans and axial deltaic systems insights from a three dimensional stratigraphic forward model many studies of foreland basins have recognized a hierarchical organization in the stacking of sequences deposited by axial deltaic and alluvial fan systems the hierarchy is often explained in terms of the competing control of eustasy and pulsed tectonic subsidence and the different frequencies at which these processes operate unravelling the relative contributions of tectonic and eustatic controls on the sequence stacking pattern is a fundamental question in foreland basin analysis yet this is difficult because of the lack of independent stratigraphic evidence in this study a three dimensional numerical model is presented which aids in the interpretation of alluvial successions in foreland basins filled by transverse and axial depositional systems under conditions of variable tectonism and eustatic sea level change the tectono sedimentary model is capable of simulating the hierarchical stratigraphic response to both eustatic and tectonic forcing and is of higher resolution than previous models of foreland basin filling numerical results indicate that the onset of tectonic activity is reflected by rapid retrogradation of both depositional systems and by widespread flooding and onlap of carbonate sediments syntectonic fluvial patterns on the axial deltaic plain are dominated by bifurcating channels swiftly relocating in response to the general rise in relative sea level induced by flexural subsidence the resulting surface morphology of the axial delta is convex upwards syntectonic eustatic sea level fluctuations result in parasequence scale packages of retrograding and prograding fan and delta sediments bounded by minor flooding surfaces and type 2 sequence boundaries incised channels are rare within the syntectonic parasequences and are formed only during phases of tectonic quiescence when eustatic falls are no longer compensated by the subsidence component in the rise in relative sea level suites of amalgamating axial channels corresponding to multiple eustatic falls delineate the resulting type 1 unconformities coarse grained incised channel fills are found in the zone between the alluvial fan fringes and the convex upward body of the axial delta as the axial streams tend to migrate towards this zone of maximum accommodation

worldwide doublets of large shallow earthquakes abstract we investigated all the pairs of mw 7 5 shallow earthquakes in the harvard catalog that occurred at a centroid distance of less than 100 km we showed that most of these pairs have similar focal mechanisms because these earthquakes generally should have focal regions in excess of 100 km diameter their rupture zones apparently intersect for all these pairs the time interval is significantly less than the time span needed for plate motion to accumulate the strain released by the first event these observations conflict strongly with quasi periodic recurrence models on which the seismic gap hypothesis is based power law recurrence fits these earthquake ob servations much better introduction many models used to forecast long term seismic hazard are based on the quasi periodic or seismic cycle hypothesis of large earthquake occurrence this hypothesis assumes that the probability of a large earthquake is low after signifi cant release of seismic energy and that danger increases only when tectonic plate motion accumulates strain sufficient for a new strong event several models have been formulated to apply this idea to long term earthquake prediction mccann

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

vostok ice core a continuous isotope temperature record over the last climatic cycle 160 000 years a continuous deuterium profile along the 160 000 year vostok ice core antarctica is interpreted in terms of atmospheric temperature changes this climatic record is the awaited terrestrial complement of the deep sea records supporting the existence of a relation between the pleistocene climate and orbital forcing

probability map of the next m 5 5 earthquakes in italy 1 the main goal of this work is to provide a probability map for the next moderate to large earthquakes m 5 5 in italy for this purpose we apply a new nonparametric multivariate model to characterize the spatiotemporal distribution of earthquakes the method is able to account for tectonics physics parameters that can potentially influence the spatiotemporal variability and tests their relative importance moreover it allows straightforward testing of a variety of hypothesis such as seismic gap cluster and poisson hypothesis the method has been applied to italian seismicity of the last four centuries for earthquakes with m 5 5 italy has been divided into 61 irregular zones representing areas with homogeneous tectonic regime resulting from active stress data besides the magnitude and the time of the earthquakes the model includes information on the tectonic stress regime the homogeneity of its orientation the number of active faults the dimension of the area and the homogeneity of the topography the time distribution of the m 5 5 earthquakes appears clustered in time for a few years after an event and then the distribution becomes similar to a memoryless poisson process leading to a time dependent probability map this map shows that the most likely regions where the next moderate to large earthquakes may occur are friuli umbria marche and part of southern apennines and the calabrian arc

a ten year earthquake occurrence model for italy the recent m w 6 3 destructive l aquila earthquake has further stimulated the improvement of the italian operational earthquake forecasting capability at different time intervals here we describe a medium term 10 year forecast model for m w 5 5 earthquakes in italy that aims at opening new possibilities for risk mitigation purposes while a longer forecast yielded by the national seismic hazard map is the primary component in establishing the building code a medium term earthquake forecast model may be useful to prioritize additional risk mitigation strategies such as the retrofitting of vulnerable structures in particular we have developed an earthquake occurrence model for a 10 year forecast that consists of a weighted average of time independent and different types of available time dependent models based on seismotectonic zonations and regular grids the inclusion of time dependent models marks a difference with the earthquake occurrence model of the national seismic hazard map and it is motivated by the fact that at the 10 year scale the contribution of time dependency in the earthquake occurrence process may play a major role the models are assembled through a simple averaging scheme whereby each model is weighted through the results of a retrospective testing phase similar to the ones carried out in the framework of the collaboratory for the study of earthquake predictability in this way the most hazardous italian areas in the next ten years will arise from a combination of distinct models that place more emphasis on different aspects of the earthquake occurrence process such as earthquake clustering historical seismic rate and the presence of delayed faults capable of large events finally we report new challenges and possible developments for future updating of the model

plate tectonic analysis of shallow seismicity apparent boundary width beta corner magnitude coupled lithosphere thickness and coupling in seven tectonic settings a new plate model is used to analyze the mean seismicities of seven types of plate boundary crb continental rift boundary ctf continental transform fault ccb continental convergent boundary osr oceanic spreading ridge otf oceanic transform fault ocb oceanic convergent boundary sub subduction zone we compare the platelike nonorogen regions of model pb2002 bird 2003 with the centroid moment tensor cmt catalog to select apparent boundary half widths and then assign 95 of shallow earthquakes to one of these settings a tapered gutenberg richter model of the frequency moment relation is fit to the subcatalog for each setting by maximum likelihood best fitting values range from 0 53 to 0 92 but all 95 confidence ranges are consistent with a common value of 0 61 0 66 to better determine some corner magnitudes we expand the subcatalogs by 1 inclusion of orogens and 2 inclusion of years 1900 1975 from the catalog of pacheco and sykes 1992 combining both earthquake statistics and the plate tectonic constraint on moment rate corner magnitudes include the following crb graphic 1 ctf graphic 2 ccb graphic 3 ocb graphic 4 and sub graphic 5 coupled lithosphere thicknesses are found to be the following crb graphic 6 ctf graphic 7 ccb graphic 8 osr graphic 9 for normal faulting and graphic 10 for strike slip otf graphic 11 and graphic 12 at low medium and high velocities ocb graphic 13 and sub graphic 14 in general high coupling of subduction and continental plate boundaries suggests that here all seismic gaps are dangerous unless proven to be creeping in general low coupling within oceanic lithosphere suggests a different model of isolated seismic fault patches surrounded by large seismic gaps that may be permanent online material global seismic subcatalogs of shallow earthquakes 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif 3 embed inline graphic 3 gif 4 embed inline graphic 4 gif 5 embed inline graphic 5 gif 6 embed inline graphic 6 gif 7 embed inline graphic 7 gif 8 embed inline graphic 8 gif 9 embed inline graphic 9 gif 10 embed inline graphic 10 gif 11 embed inline graphic 11 gif 12 embed inline graphic 12 gif 13 embed inline graphic 13 gif 14 embed inline graphic 14 gif

thorough assessment of dna preservation from fossil bone and sediments excavated from a late pleistocene holocene cave deposit on kangaroo island south australia fossils and sediments preserved in caves are an excellent source of information for investigating impacts of past environmental changes on biodiversity until recently studies have relied on morphology based palaeontological approaches but recent advances in molecular analytical methods offer excellent potential for extracting a greater array of biological information from these sites this study presents a thorough assessment of dna preservation from late pleistocene holocene vertebrate fossils and sediments from kelly hill cave kangaroo island south australia using a combination of extraction techniques and sequencing technologies ancient dna was characterised from over 70 bones and 20 sediment samples from 15 stratigraphic layers ranging in age from 20 ka to 6 8 ka a combination of primers targeting marsupial and placental mammals reptiles and two universal plant primers were used to reveal genetic biodiversity for comparison with the mainland and with the morphological fossil record for kelly hill cave we demonstrate that kelly hill cave has excellent long term dna preservation back to at least 20 ka this contrasts with the majority of australian cave sites thus far explored for ancient dna preservation and highlights the great promise kangaroo island caves hold for yielding the hitherto elusive dna of extinct australian pleistocene species

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

results from a new model of river basin evolution this paper briefly describes a model of the erosional development of catchments and their channel networks the model differentiates between the dominant transport processes in hillslope and channels the development of channels and hillslopes occurs in an integrated manner as a function of physically observable mechanisms the growth of a river basin is qualitatively described the model concepts are used to study the basin during periods of growth transient periods as well as during dynamic equilibrium this leads to hypotheses about the relationship between slopes relief tectonic uplift erodability runoff and catchment area it is shown that the model leads to very reasonable and desirable behaviour of hillslopes during retreat and degradation

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

rapid sea level fall and deep ocean temperature change since the last interglacial period we have dated huon peninsula papua new guinea and barbados corals that formed at times since the last interglacial period applying both 230 th and 231 pa dating techniques as a test of age accuracy we show that marine isotope stage mis 5e ended prior to 113 1 8 0 7 kyr when sea level was 319 m during mis 5b sea level was 357 m at 92 6 8 0 5 kyr having dropped about 40 m in approximately 10 kyr during the mis 5c 5b transition sea level then rose more than 40 m during the mis 5b 5a transition also in about 10 kyr mis 5a lasted until at least 76 2 8 0 4 kyr at a level of 324 m at that time combined with earlier data that places mis 4 sea level at 381 m at 70 8 kyr our late mis 5a data indicate that sea level fell almost 60 m in less than 6 kyr 10 6 m kyr during the mis 5 4 transition the magnitude of the drop is half that of the glacial interglacial amplitude and approximatelyequivalent to the volume of the present dayantarctic ice sheet during this interval the minimum average rate of net continental ice accumulation was 18 cm yr likely facilitated by efficient moisture transport from lower latitudes at three specific times 60 6 8 0 3 50 8 8 0 3 and 36 8 0 2 kyr during mis 3 sea level was between 385 and 374 m sea level then dropped to 3107 m at 23 7 8 0 1 kyr early in mis 2 before dropping further to last glacial maximum lgm values and then rising to present values during the last deglaciation times of rapid sea level drop correspond to times of high winter insolation at low northern latitudes and high winter latitudinal gradients in northern hemisphere insolation supporting the idea that these factors mayhave resulted in high water vapor pressure in moisture sources and efficient moisture transport to high latitude glaciers therebycontributing to glacial buildup we combined our sea level results with deep sea n 18 o records as a means of estimating the temperature and ice volume components in the marine n 18 o record this analysis confirms large deep ocean temperature shifts following mis 5e and during termination i deep ocean temperatures changed bymuch smaller amounts between mis 5c and 2 maximum temperature shift in the deep pacific is about 2 whereas the shift at a site in the atlantic is 4 under glacial conditions temperatures at both sites are near the freezing point the shift in the atlantic is likelycaused bya combination of changing proportions of northern and southern source waters as well as changing temperature at the sites where these deep waters form

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

basin sedimentation and the growth of prograding deltas a theoretical model is developed for the infilling of a basin by the progradation of a delta the model simulates four mechanisms for the transfer of sediment from the land to the sea 1 bed load dumping along the delta front 2 hemipelagic sedimentation under the seaward flowing river plume 3 proximal slope bypassing by turbidity currents and 4 the combined effects of both short term wave and tidal action and long term creep and small slides downslope diffusion of the accreting sediment mass the general model is of relatively low precision useful for predicting basin infilling on time scales greater than a few hundred years the river plume portion of the model can predict sedimentation on time scales of less than a year and is designed to reflect the dynamics of a free two dimensional buoyant jet that transports a composite size population of suspended particles the general model allows the prediction of lithologies changing with time and space the model has been used to simulate infilling processes for knight and bute inlets two grabenlike fjord basins along the coast of british columbia model simulations of delta progradation over the last 10 000 years favorably predicted the modern seafloor bathymetry and sediment accumulation rates to within a factor of 2 of measured 210pb 137cs and sediment trap rates

global omori law decay of triggered earthquakes large aftershocks outside the classical aftershock zone 1 triggered earthquakes can be large damaging and lethal as evidenced by the1999 shocks in turkey and the 2001 earthquakes in el salvador in this study earthquakes with ms 7 0 from the harvard centroid moment tensor cmt catalog are modeled as dislocations to calculate shear stress changes on subsequent earthquake rupture planes near enough to be affected about 61 of earthquakes that occurred near defined as having shear stress change 0 01 mpa the ms 7 0 shocks are associated with calculated shear stress increases while 39 are associated with shear stress decreases if earthquakes associated with calculated shear stress increases are interpreted as triggered then such events make up at least 8 of the cmt catalog globally these triggered earthquakes obey an omori law rate decay that lasts between 7 11 years after the main shock earthquakes associated with calculated shear stress increases occur at higher rates than background up to 240 km away from the main shock centroid omori s law is one of the few time predictable patterns evident in the global occurrence of earthquakes if large triggered earthquakes habitually obey omori s law then their hazard can be more readily assessed the characteristic rate change with time and spatial distribution can be used to rapidly assess the likelihood of triggered earthquakes following events of ms 7 0 i show an example application to the m 7 7 13 january 2001 el salvador earthquake where use of global statistics appears to provide a better rapid hazard estimate than coulomb stress change calculations

a reevaluation of cosmogenic 36cl production rates in terrestrial rocks we have measured 36cl in a suite of 33 rock samples having well constrained exposure histories and ages the 36cl production parameters were estimated by minimizing the squared deviations between the 36cl and independent ages yielding the following production parameters spallation and muon production from ca 2940 200 atoms 36cl mole ca 1 yr 1 spallation from k 6020 400 atoms 36cl mole k 1 yr 1 and neutron production in air 586 40 fast neutrons g air 1 yr 1 the new production constants for spallation on ca and thermal neutron activation are in good agreement with previous results but that for spallation on k is about 50 larger the past decade has seen a rapid growth in the application of terrestrial cosmogenic nuclides produced by cosmic ray particles within rocks at the earth surface nuclear cross sections particularly for reactions initiated by neutrons and muons are not known with sufficient accuracy so production rates for these nuclides must be empirically calibrated using independently dated geological samples direct production estimates for 36cl were first obtained by zreda et al 1991 who measured 36c1 in mineral separates from granitic boulders on moraine crests at chiatovitch creek in the eastern white mountains of california and nevada this data set was the best available at the time but since then several factors have prompted a reevaluation of the 36cl production rates one is that zreda et al 1994 have shown that there can be significant scatter of the cosmogenic ages of individual glacial boulders toward ages younger than that of the moraine due to soil erosion a second factor is that a much wider range of samples is now available for this purpose finally recent theoretical advances in calculating production by thermal neutron absorption liu et al 1994 now permit more realistic calibration of this reaction

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