geological and oceanographic perspectives on event bed formation during hurricane katrina 1 storm deposits in ancient shelf sediments typically form thick sequences of interbedded sand and mud deposited during shoreline regression whereas modern shelf sediments are generally thin veneers deposited during shoreline transgression in this paper we present a preliminary comparison between ancient and modern storm beds deposited in these disparate contexts hurricane katrina deposited a storm bed on the louisiana shelf with a maximum observed thickness of 0 58 m which thinned to approximately 0 1 m at 200 km west of landfall this thickness is similar to event beds observed in both ancient and modern sediments using data for tropical cyclone landfalls in the gulf of mexico we estimate the return time for a storm of this size to be 40 50 years in this region this estimated frequency for deposition of storm beds is useful in evaluating ancient storm sequences that were deposited during similar climatic conditions

esr isochron dating of the nojima fault gouge southwest japan using icp ms an approach to fluid flow events in the fault zone

direct dating of quaternary phreatic maar eruptions by luminescence methods the suitability of quartz optically stimulated luminescence osl and feldspar infrared stimulated luminescence irsl for the direct dating of phreatic eruptions was tested on examples from the eifel volcanic field germany the mean irsl age of 11 6 0 5 ka for ulmener maar tephra is in excellent agreement with the independent age control 11 0 1 ka but the mean osl age of 14 2 0 6 ka overestimates the known age by 3 ka for meerfelder maar tephra consistent irsl mean 74 9 5 0 ka and osl ages 74 9 5 5 ka have been observed the consistent results from meerfelder maar imply that the overestimation observed for ulmener maar quartz osl might not be relative to the eruption age but rather represents a small absolute offset in samples taken from deposits of the eruption of laacher see volcano no resetting of the osl signal and highly scattered irsl estimates were found this implies that phreatomagmatic eruptions are less well suited for this dating approach compared to pure phreatic maar eruptions where the effect of high pressure shock waves probably dominates the process of resetting the luminescence signal

optical dating of tsunami laid sand from an oregon coastal lake abstract optical ages for five samples of tsunami laid sand from an oregon coastal lake were determined using an infrared optical dating method on k feldspar separates and as a test of accuracy compared to ages determined by ams 14c dating of detrital plant fragments found in the same beds two optical ages were about 20 younger than calibrated 14c ages of about 3 1 and 4 3 ka correction of the optical ages using measured anomalous fading rates brings them into agreement with the 14c ages the approach used holds significant promise for improving the accuracy of infrared optical dating methods luminescence data for the other three samples result in optical age limits much greater than the 14c ages these data provide a textbook demonstration of the correlation between scatter in the luminescence intensity of individual sample aliquots and their normalization values that is expected when the samples contain sand grains not adequately exposed to daylight just prior to or during deposition and burial thus the data for these three samples suggest that the tsunamis eroded young and old sand deposits before dropping the sand in the lake

uranium series nuclides in the golden fault colorado u s a dating latest fault displacement and measuring recent uptake of radionuclides by fault zone materials abstract concentrations and isotopic ratios of u th and ra were measured in a fault zone near golden colorado where major displacement occurred between about 190 and 615 ka faulting created new surfaces for leaching and provided the pathways for u rich ground water uranium and230th the latter produced by the decay of dissolved234u are adsorbed by fault gouge hematite stained sand and brecciated sand and claystones the observed u enrichment is as much as six times baseline value and the simultaneous enrichment of230th is estimated at about ninefold relative to238u the adsorption of radionuclides chemically analogous to th such as pu iv and np and237np decay products on fault zone materials would contribute to the immobilization of high level radioactive waste in the vicinity of a repository in the event of leakage from engineered barriers into fractured rock mass

slip rate estimate and past earthquakes on the doruneh fault eastern iran summary the doruneh fault with a length of 600 km is one of the longest and most prominent faults in iran it performs an important role in the regional tectonics but has no record of large earthquakes the geomorphology of the doruneh fault contains numerous indications of cumulative left lateral slip over various scales we describe three sites where late quaternary landforms are displaced by the fault a an incised alluvial fan near the village of uch palang is displaced by 800 850 m b the kuh e teagh ahmad fold is composed of folded quaternary gravels and is displaced by 200 400 m c a sequence of three terraces of the shesh taraz river are displaced left laterally by a maximum of 25 m infrared stimulated luminescence irsl dating of the uppermost shesh taraz river terrace gives a deposition age of 10 ka which correlates with changes in global climate 10 12 ka ago and provides a provisional slip rate estimate of 2 4 0 3 mm yr 1 no major recent or historical earthquakes are recorded on the doruneh fault relatively fresh scarps and partially infilled fractures appear to be the preserved surface ruptures from an earthquake event of unknown age a series of small streams showing left lateral displacements of 3 to 5 5 m with an average slip of 4 7 m record the possible magnitude of slip during this earthquake which from scaling relationships would have had an m w of 7 5 and ruptured the fault over a length of 100 km at the estimated slip rate of 2 5 mm yr 1 the average recurrence time between large magnitude earthquakes on the doruneh fault is 2000 yr

recovery of stress during the interseismic period around the seismogenic fault of the 1995 m w 6 9 kobe earthquake japan

the ordovician sebree trough an oceanic passage to the midcontinent united states the sebree trough is a relatively narrow shale filled sedimentary feature extending for several hundred kilometers across the middle and late ordovician carbonate platform of the midcontinent united states the dark graptolitic shales within the trough stand in contrast to the coeval bryozoan brachiopod echinoderm rich limestones on the flanking platforms we infer from regional stratal patterns thickness and facies trends and temporal relations established by biostratigraphy and k bentonite stratigraphy that the sebree trough initially began to develop during late turinian to early chatfieldian time mohawkian series as a linear bathymetric depression situated over the failed late precambrian early cambrian reelfoot rift rising sea level and positioning of a subtropical convergence zone along the southern margin of laurentia caused the rift depression to descend into cool oxygen poor phosphate rich oceanic waters that entered the southern reaches of the rift from the iapetus ocean the trough apparently formed in a system of epicontinental estuarine circulation marked by a density stratified water column trough formation was accompanied by cessation of carbonate sedimentation deposition of graptolitic shales development of hardground omission surfaces substrate erosion and local phosphogenesis the carbonate platforms on either side of the trough are dominated by bryozoan brachiopod echinoderm grainstones and packstones that were deposited in zones of mixing where cool nutrient rich waters encountered warmer shelf waters concurrently lime mudstone and wackestone were deposited shoreward northern illinois wisconsin iowa minnesota michigan in warmer more tropical shallow seas coeval upward growth of the flanking carbonate platforms sustained and enhanced development of the trough shale facies five widespread diachronous late mohawkian and cincinnatian omission surfaces are present in the carbonate facies of the midcontinent these surfaces include sub deicke k bentonite ds1 top of black river limestone ds2 base and top of the guttenberg limestone member of the decorah formation ds3 and ds4 and top of the trenton limestone ds5 some of the surfaces correspond to previously described depositional sequence boundaries all five surfaces which embody deepening phases on top of highstand systems tracts converge in the sebree trough indicating that the trough was a long lived feature and was the source of eutrophic waters that episodically spread across the adjacent platforms terminating carbonate production late turinian and early chatfieldian incipient drowning episodes were followed by a final drowning event that began in the sebree trough during the late chatfieldian climacograptus spiniferus zone and reached southernmost minnesota and other regions far within the platform interior by richmondian time amorphognathus ordovicicus zone

the behavior of u and th series nuclides in the estuarine environment rivers carry the products of continental weathering and continuously supply the oceans with a broad range of chemical constituents this erosional signature is however uniquely moderated by biogeochemical processing within estuaries estuaries are commonly described as complex filters at land sea margins where significant transformations can occur due to strong physico chemical gradients these changes differ for different classes of elements and can vary widely depending on the geographic location u and th series nuclides include a range of elements with vastly different characteristics and behaviors within such environments and the isotopic systematics provide methods for investigating the transport of these nuclides and other analog species across estuaries and into the coastal ocean there are numerous types and definitions of estuaries see dyer 1973 in this paper it is simply considered to be a region where freshwater and seawater mix to emphasize the chemical focus of the issues involved here this region can either be contained within a river channel or extend onto the shelf with effects often extending well into an adjoining ocean basin fairbridge 1980 these are complex ecological biogeochemical and hydrodynamic systems with strong gradients in the concentrations and composition of micro and macro particulate matter as well as dissolved organic and inorganic species particle reactive radionuclides and trace elements being transported across estuaries are subject to partitioning between the dissolved colloidal and particulate phases the variable chemical nature of the u and th series radionuclides is evident in their distributions in an estuarine environment such radionuclides can effectively serve as tracers to identify the sources fate and transport of particles and colloids as well as other pollutants that behave similarly to these nuclides these nuclides also have a wide range of half lives that can be used to examine processes over various time scales for example th and ra daughter isotopes have

criteria for complete zeroing of esr signals during faulting of the san gabriel fault zone southern california in using electron spin resonance esr to date the time of the last movement on a fault it is essential to demonstrate that the esr signal was fully zeroed at the time of faulting if the signal was not completely reset then the esr age obtained will be too great we have refined the criteria for complete zeroing of esr signals at the time of fault movement samples of fault rocks were collected from surface outcrops of the san gabriel fault zone in the little tujunga region near los angeles southern california using quartz grains of 250 m the estimated ages for either e or ohc signals in all fault rock samples analyzed decrease with grain size down to a plateau value for particles smaller than some critical grain size in some cases the al signal in the smallest grains yields the same age as the plateau age of either the e or ohc signal plateau ages of reactivated younger gouges were indeed smaller than those of the older fault host rocks within the plateau region different grain size fractions show different radiation sensitivity for a single esr signal but all converge to the same de equivalent dose value this indicates that the complete resetting probably occurred during fault movement the depth of fault rocks during fault movement can be estimated from uplift rates and the esr ages the estimated uplift rates was about 0 3 cm yr for the holocene and 0 03 cm yr for the late pleistocene menges et al 1979 the estimated plateau esr ages ranged from 1200 to 135 ka the depths at the time of the last fault movements in the little tujunga region were in the range of 68 360 m the measured maximum horizontal stresses at this depth in southern california range from 5 to 10 mpa for a depth of 70 m the calculated vertical stress is 1 16 mpa and measured maximum horizontal stress is about 5 mpa the angle between the strike of the san gabriel fault and the direction of maximum horizontal stress is about 85 using above values calculated shear stress on the fault is about 0 67 mpa and the normal stress to the fault is about 5 mpa if we assume mean displacements of 4 cm m 4 to 1 m m 7 these conditions were sufficient to reset esr signals in quartz below critical grain size at the time of fault activity

the distribution of apparent dose as determined by optically stimulated luminescence in small aliquots of fluvial quartz implications for dating young sediments abstract we noted recently murray et al 1995 that quartz samples taken from in channel fluvial deposits have apparent doses ranging over several orders of magnitude we suggested that these dose distributions are best explained by a mixture of a small number of poorly bleached grains and a larger number of well bleached grains in this paper we examine the distribution of apparent dose in small aliquots each composed of 2000 grains of different particle size fractions 63 90 m 90 125 m 125 180 m 180 212 m 212 250 m diameter from two samples collected from the murrumbidgee river new south wales australia the samples are of known burial age the first being 70 years old and the second being its modern equivalent 0 2 gy the difference in the lowest apparent dose in the two samples is considered to be the result of their different burial times we suggest a method for dating recently deposited

variation in the composition and partitioning of adsorbed cations at a brine contaminated crude oil production facility in southeastern louisiana usa abstract the first geological materials impacted by oil field wastes released into near surface environments in southern louisiana usa are typically clays and silts clay minerals within these siliciclastic sediments have the potential for altering the composition of produced water wastes through cation exchange the general relations between the composition of adsorbed cations and interstitial water salinity in brine contaminated samples from a site in southeastern louisiana are consistent with previous studies of multicomponent exchange in groundwater systems of varying salinity the divalent cations ca and mg dominate as adsorbed cations at low salinities calculated interstitial water compositions assuming exchange equilibrium are consistent with the source of contamination being produced waters having na as the dominant dissolved cation followed by ca rather than some other type of saline waste the calculated partitioning for ba indicates that in low to moderate salinity pore waters ba and by extension ra are nearly quantitatively adsorbed on the clays and would be of low mobility in a physically active groundwater system however at the elevated salinities typical of many produced waters ba and ra are not preferentially adsorbed

optically stimulated luminescence dating of sediments over the past 200 000 years optical dating of sediment using optically stimulated luminescence has become important for studying earth surface processes and this technique continues to develop rapidly a group of closely linked luminescence methods can be used to estimate the time since grains of quartz and feldspar were last exposed to daylight by detecting their subsequent response to environmental ionizing radiation exposure the technique is well suited to the dating of deposits as young as one year to several hundred thousand years recent technical developments have established a dating protocol with improved precision a high degree of reliability and an in built means to detect incomplete signal removal during deposition this approach has been extended to age estimation for single grains opening up a wider range of potential environments and new possibilities for understanding postdepositional grain movement ongoing research offers the possibility of significant age range extension and novel applications including low t

alternative chronologies for late quaternary last interglacial holocene deep sea sediments via optical dating of silt sized quartz abstract we summarize the results of a test on the potential of optical dating for the age assessment of late quaternary deep sea sediments our approach combines a single aliquot regeneration sar protocol for equivalent dose d e estimation on fine silt sized quartz with a time dependent evaluation of supported and unsupported long lived radioisotopes within the deposited sediment matrix for this purpose nine samples from two independently dated deep sea cores from the indian ocean were obtained the sar analysis resulted in mean d e estimates with precisions ranging from 0 9 to 3 7 combination of these data with measured radioisotope concentrations resulted in stratigraphically sensible ages ranging from ca 7 to 120 ka these ages exhibit good agreement with existing chronologies for the cores based on radiocarbon age determinations and correlation of key volcanic palaeoecological and isotopic events optical dating may provide an important additional dating method for late quaternary deep sea sediments

thermoluminescence dating of fault scarp derived colluvium deciphering the timing of paleoearthquakes on the weber segment of the wasatch fault zone north central utah the timing of middle to late holocene faulting on the weber segment of the wasatch fault zone utah is constrained by thermoluminescence tl and radiocarbon age estimates on fine grained fault related colluvial sediments the stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges deposited in response to three separate faulting events the oldest of which buried a soil developed on a middle holocene debris flow thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine grained colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology a synthesis of the tl and 14c age estimates indicate that these three faulting events occurred sometime between 4500 and 3500 between 3200 and 2500 and between 1400 and 1000 years ago detailed investigation of a sequence of fine grained scarp derived distal colluvium shows that much of the sediment was deposited during 600 year intervals immediately after faulting the sedimentation rate of colluvium is inferred to increase shortly after faulting and tl dating of these sediments provides additional information to constrain the timing of faulting events

testing an approach to osl dating of late devensian glaciofluvial sediments of the british isles in the british and irish isles the understanding of expansion and retreat of the last ice sheet in marine isotope stage mis 2 has been hindered by a lack of chronological control for the timing of its maximum extent and subsequent retreat stages in this research a suite of lithofacies from a former distal ice marginal sandur at orrisdale isle of man were identified and selected for optically stimulated luminescence dating different size fractions of quartz grains were extracted from selected lithofacies types with the aim of identifying which depositional environments and grain size fractions are best suited for optical dating tests have been undertaken to identify the luminescence properties of this quartz including preheat dose recovery and constant wave optically stimulated luminescence osl decay curve fitting equivalent dose distributions for all samples were wide and positively skewed indicative of heterogeneous bleaching a comprehensive statistically based decision making protocol has been defined in order to find the appropriate statistical model for burial dose estimation ages in the range of 17 14 ka have been obtained which agree with the expected geologically constrained chronology the orrisdale formation is contemporaneous with heinrich event 1 and the killard point stadial identified in eastern ireland ca 16 4 ka the suggested approach for osl dating of glaciofluvial sediments has the potential for much wider application to high latitude or temperate areas where there is an abundance of such sediments and where improved chronological control is much needed copyright 2009 john wiley sons ltd

preservation potential of sedimentary event layers preservation potential of sedimentary event layers e g ash layers or tempestites is a function of net sedimentation rate and biogenous mixing rate previous studies that have used an inverse peclet number to scale the problem in terms of advection or diffusion are in error due to the improper inclusion of the surface mixed layer thickness as the sole length scale herein focus is on time scales if the transit time i e time required to advect the signal through the biologically active zone is less than the dissipation time i e time required to destroy the signal then some fraction of the original signal is preserved a simple quantitative model based on the diffusion analogy of sediment mixing estimates the actual percentage of preserved signal under various combinations of sedimentation rate mixing rate and event layer thickness

chronostratigraphy of a loess palaeosol sequence in bialy kościol poland using osl and radiocarbon dating abstract optically stimulated luminescence osl is particularly suitable for providing a numerical timescale necessary for loess to be useful in climatic reconstructions it is widely accepted that quartz osl dating using the single aliquot regenerative dose sar procedure usually yields reliable ages the current work presents osl ages derived from coarse 90 125 m and medium 45 63 m quartz grain size fractions and post ir ir290 for polymineral fine grains 4 11 m in addition to dating analyses of the magnetic susceptibility grain size distribution carbonate and organic carbon content were conducted previously the profile was dated using single aliquot optically stimulated luminescence osl applied to coarse grained quartz fraction 90 125 m only using the central age model this analysis yielded unexpectedly young ages for the deepest part of the bialy ko ciol loess profile in the current study we investigate the differences between the previously obtained results and new results obtained for medium grained quartz and polymineral fine grain fractions ages obtained for coarse and medium fractions show no differences up to the equivalent dose of about 150 gy in contrast to the younger samples for the five oldest samples we observe that the results obtained for coarse grained quartz yield ages lower that the medium grained quartz those differences reach 25 for the two oldest samples in addition the polymineral fine grain fraction yields results very similar to the previously obtained coarse grained quartz ages with the exception of the two oldest samples where the polymineral fraction gives much older results those differences between the ages of the two grain size fractions can arise from post depositional grain size dependent sediment translocation processes due to pedo and bio turbation and a different efficiency of bleaching of the post ir signal those results obtained for lithostratigraphic units ii and i correspond to mois 4 and 5 respectively confirming the earlier established mois chronology and strengthen the chronological correlation of the loess profile at bialy ko ciol with other loess profiles in europe

osl dating of coarse grain fluvial quartz using single aliquot protocols on sediments from ne peloponnese greece abstract optical ages of quartz extracts in holocene sediments from the north eastern peloponnese greece are reported the single aliquot regenerative dose protocol proposed by murray and wintle 2000 radiation measurements 32 57 73 was used to estimate the equivalent dose in these samples a large inter aliquot scatter in d e values was observed for all samples this is ascribed to heterogeneous bleaching of the samples at deposition to estimate a d e for age calculation a technique is suggested based on the analysis of the d e scatter obtained from nine different quartz samples which were artificially bleached and irradiated this procedure is especially useful when the sample quantity is limited the optical age estimates increase with sampling depth an average aggradation rate of 1 5 mm yr is derived using the osl ages this value is consistent with the known uplift rate of 1 2 mm yr

optical dating of holocene sediments from a variety of geomorphic settings using single grains of quartz this paper presents an improved method for the optical dating of holocene sediments from a variety of geomorphic settings we have measured the equivalent dose de in individual grains of quartz using green laser light for optical stimulation and have simulated the de distributions for multiple grain synthetic aliquots using the single grain data for 12 samples of known independent age we show that application of a minimum age model to the single grain and small 10 grain aliquot de data provides the most accurate estimate of the burial dose for nine of the samples examined 3 aeolian 5 fluvial and 1 marine the weighted mean de as obtained using the central age model gives rise to burial age overestimates of up to a factor of 10 for these nine samples whether single grains small aliquots or large 100 grain aliquots are used for the other three samples two aeolian and one fluvial application of either the minimum age model or the central age model to the single grain small aliquot and large aliquot de data yields burial ages in accord with the independent age control we infer that these three samples were well bleached at the time of deposition these results show that heterogeneous bleaching of the optical dating signal is commonplace in nature and that aeolian transport offers no guarantee that the sample will be well bleached at the time of deposition we also show that grains sensitive to infrared ir stimulation can give rise to low de values which will result in significant underestimation of the burial dose and hence of the age of deposition we demonstrate that use of a modified single aliquot regenerative dose protocol incorporating ir stimulation prior to green light stimulation deals effectively with contamination by ir sensitive grains we conclude that application of the modified protocol to single grains or small aliquots of quartz using the lowest de population to estimate the burial dose is the best means of obtaining reliable ages for holocene sediments from a wide range of depositional environments d 2003 elsevier b v all rights reserved

timing of recent out of sequence active deformation in the frontal himalayan wedge insights from the darjiling sub himalaya india recent studies of india eurasia convergence suggest that the entire convergence in the himalayan wedge is almost exclusively accommodated along its basal detachment fault main himalayan thrust mht and its near surface equivalent main frontal thrust mft using direct dating of fault zone gouge and strath terrace deposits we conclude the following 1 the present mountain front in the darjiling sub himalaya was emplaced by ca 40 ka 2 out of sequence deformation on surface breaking faults north of the mft in the darjiling sub himalaya began ca 20 ka and has probably continued since 3 the tista river responded to the ca 20 ka deformation by migrating 150 m eastward average rate 13 mm yr 1 and by incising 48 m vertically average rate 4 4 mm yr 1 creating unpaired disjointed strath terraces between 11 3 1 3 ka and 1 4 0 3 ka out of sequence surface breaking faults in the himalaya indicate partial accommodation of active convergence within the himalayan wedge using the results from the bhuj earthquake of 2001 we suggest that active deformation along the out of sequence faults is a potential seismic hazard in the himalaya and himalayan seismic hazard models must account for this we also propose a conceptual model for active deformation in the himalaya

structural analysis of a previously unknown active fault that triggered the 2013 mw 5 8 awajishima earthquake southwest japan the m w 5 8 awajishima earthquake occurred on 13 april 2013 in southwest awaji island 25 km southwest of the epicenter of the 1996 m w 6 8 kobe earthquake southwest japan analyses of aerial photographs and 3d perspective images field investigations and structural analysis of fault rocks reveal that 1 a previously undocumented fault here called the yamada fault strikes northwest southeast and dips southwest at 86 along a topographic lineament at the geological boundary between mesozoic granitic rocks and the late pliocene quaternary osaka group composed of interbedded sandstone and mudstone 2 the main shear zone of the yamada fault consists of a fault core with a 10 cm wide zone of fault gouge generally 1 5 cm a fault breccia zone of 100 cm wide and a damage zone of 10 50 m wide composed of cataclastic rocks and fractures 3 foliations characterized by s c fabrics that have developed in the shear zone indicate a dominantly thrust fault sense consistent with that revealed by the focal mechanism and 4 coseismic surface ruptures occurred locally along the main trace of the yamada fault consisting of numerous short fissures ranging in length from centimeters to several meters and concentrated in a zone 5 m wide our findings show that the newly identified yamada fault is an active fault and that it is probably the fault on which the 2013 m w 5 8 awajishima earthquake occurred therefore it is necessary to construct a fault model to better understand the deformation characteristics of the seismogenic source fault and for reassessing the seismic hazards on the densely populated awaji island of southwest japan

seismic moment and recurrence microstructural and mineralogical characterization of rocks in carbonate fault zones and their potential for luminescence and esr dating abstract the important question of absolute dating of seismic phenomena has been the study of several researchers over the past few decades the relevant research has concentrated on energy traps of minerals such as quartz or feldspar which may accumulate chronological information associated with tectonic deformations however the produced knowledge so far is not sufficient to allow the absolute dating of faults today luminescence and electron spin resonance esr dating methods could be seen as offering high potential for dating past seismic deformed features on timescales ranging from some years to even several million years this preliminary study attempts to establish the potential of three different carbonate fault zones hosting fault mirror like structures to be used in luminescence and esr dating based on their microstructural mineralogical and palaeo maximum temperatures analysis the results indicated that the collected samples can be considered datable fault rock materials since they contain suitable minerals quartz for luminescence and esr dating have experienced repeated cataclastic deformation and have been subject to various physical and chemical processes as well as pressure and temperature conditions

rapid coastal subsidence in the central ganges brahmaputra delta bangladesh since the 17th century deduced from submerged salt producing kilns the densely populated low lying ganges brahmaputra delta is highly vulnerable to global sea level rise in order to estimate the rate of subsidence of the delta we examined submerged salt producing kiln sites in the coastal sundarbans a huge unesco protected mangrove forest these kilns were built just above the winterly spring high tide level of the time but their bases are currently located 155 cm below the corresponding modern level according to optically stimulated luminescence osl dating the kilns were last fired 300 yr ago and salt production was terminated by a catastrophic event that affected the kiln sites at different levels and locations 14 c ages of charcoal at the kilns bases and associated mangrove stump horizons support the osl dates based on the elevations and ages the 300 yr average rate of sinking of the outer delta is 5 2 1 2 mm yr which includes 0 8 mm yr of eustatic sea level rise with the expectation of further acceleration of sea level rise the already present problematic situation will be aggravated and only prudent control of sediment accretion will keep southern bangladesh above sea level

assessment of fault activity by esr dating of fault gouge an example of the 500 m core samples drilled into the nojima earthquake fault in japan abstract fault gouge in the 500 m core samples drilled into the nojima fault which caused the 1995 kobe earthquake was used for electron spin resonance esr dating the fault gouge was located at a depth of 388 4 m however all the esr signals in the fault gouge had been incompletely reset by the 1995 faulting as a result of esr dating using quartet esr signals in montmorillonite the youngest esr age about 0 15 0 29 ma is obtained from the 0 3 mm sheet part of the fault gouge just on the fault plane this age corresponds to middle late pleistocene for protection against earthquake disaster active faults which have moved since late pleistocene have high seismic risk so it is important to evaluate the esr age of the fault gouge even though it does not always mean the age of the latest fault movement meanwhile the oldest age is about 0 39 0 73 ma obtained from the 33 50 mm part this age may mean not only the production age but also the age of the first fault movement along the fault plane

applicability of esr dating using multiple centres to fault movement the case of the itoigawa shizuoka tectonic line a major fault in japan abstract no direct method for dating the fault movement has been hitherto established except esr dating whose applicability is disputed however the most serious question in esr dating is whether accumulated esr signals are completely reset at the time of fault movement when the defect centres are partially preserved at the time of previous faulting the date obtained is uncertain we have shown fukuchi et al 1985 1986 however that we can judge correctly whether esr signals were completely reset or not when the esr signal counting is done for multiple esr centres of different stabilities for resetting from the data for completely reset centres actual date of fault movement can be calculated this multiple centre method was tested with samples whose esr signal intensities are judged to be about zero at the time of fault movement the result which confirms the applicability for the fault movement dated back to 100 ka bp is presented in this paper

new age estimates for the palaeolithic assemblages and pleistocene succession of casablanca morocco marine and aeolian quaternary sediments from casablanca morocco were dated using the optically stimulated luminescence osl signal of quartz grains these sediments form part of an extensive succession spanning the pleistocene and contain a rich faunal and archaeological record including an acheulian lithic assemblage from before the brunhes matayama boundary and a homo erectus jaw from younger cave deposits sediment samples from the sites of reddad ben ali oulad j mel sidi abderhamane and thomas quarries have been dated in order to assess the upper limits of osl the revision of previously measured mammalian tooth enamel electron spin resonance esr dates from the grotte des rhinoceros oulad hamida quarry 1 incorporating updated environmental dose rate measurements and attenuation calculations also provide chronological constraint for the archaeological material preserved at thomas quarries several osl age estimates extend back to around 500 000 years with a single sample providing an osl age close to 1 ma in magnetically reversed sediments these luminescence dates are some of the oldest determined and their reliability is assessed using both internal criteria based on stratigraphic consistency and external lithostratigraphic morphostratigraphic and independent chronological constraints for most samples good internal agreement is observed using single aliquot regenerative dose osl measurements while multiple aliquot additive dose measurements generally have poorer resolution and consistency novel slow component and component resolved osl approaches applied to four samples provide significantly enhanced dating precision and an examination of the degree of signal zeroing at deposition a comparison of the osl age estimates with the updated esr dates and one u series date demonstrate that this method has great potential for providing reliable age estimates for sediments of this antiquity we consider the cause of some slight age inversion observed at thomas quarries and provide recommendations for further luminescence dating within this succession

thickness of the seismic slip zone this article reviews geologic and other evidence constraining the thickness of the principal slip zone psz that accommodates the bulk of coseismic shear displacement during an individual rupture event surface deformation from rupturing may occupy swaths tens of meters or more in width but trenches across active faults generally reveal that incremental slip is accommodated by a psz that is tens of centimeters or less in thickness geomorphic evidence coupled with the observations from trenching suggest a psz may stay well localized for distances of several kilometers through many rupture episodes mine exposures and exhumed fault zones demonstrate that pszs separating different lithologies within the fault core although contained within damage zones of variably fractured rock ranging up to hundreds of meters in thickness often comprise just a few centimeters of gouge ultracataclasite that have accommodated large finite displacements 1 km microstructural studies demonstrate incremental slip localized still further down to 1 10 mm as do other fault rock assemblages slickensides and slickenfibers fault veins of pseudotachylyte friction melt intravein septa in hydrothermal fault infills the accumulated evidence indicates that localization of coseismic shearing to less than 10 cm on planar faults is widespread throughout the crustal seismogenic zone with extreme localization to less than 1 cm not uncommon however some distributed coseismic shear may also develop especially at rupture irregularities coseismic reduction of shear resistance from friction melting t 1000 c or from transient thermal pressurization of aqueous fluids t 100 c requires slip during moderate to large earthquakes u 1 m to be restricted to narrow zones respectively a few centimeters or tens of centimeters in thickness given the evidence for slip localization the apparent scarcity of pseudotachylyte suggests either that seismic friction melting is a rare phenomenon or that pseudotachylyte is only rarely preserved in recognizable form within mature hydrated fault zones

luminescence dating of fluvial sediments and overbank deposits from gossau switzerland fine grain dating abstract last glacial fluvial sediments and overbank deposits from gossau switzerland have been investigated applying infrared stimulated luminescence irsl and thermoluminescence tl to polymineral fine grains age estimates have been determined using irsl and tl broad band blue yellow and uv emissions the irsl dates are mainly consistent with independent dating results while most of the tl measurements result in age overestimations caused by insufficient bleaching before deposition

luminescence studies on neotectonic events in south central kumaun himalaya a feasibility study abstract results of a feasibility study on luminescence dating of neotectonic events as recorded in fault gouges and buried soils formed on landslide debris are reported it is suggested that clay mineralogical data on illite and chlorite can provide a reasonable estimate on the thermal excursion and hence on resetting of the luminescence clock during faulting the thermoluminescence ages are consistent with the available radiocarbon ages and have been used to infer that naini lake was formed at ca 40 50 ka

luminescence dating of fault related alluvial fan sediments in the southern arava valley israel abstract infrared stimulated luminescence irsl from coarse grained alkali feldspars was used to date alluvial and colluvial deposits from nahal shehoret situated in the hyperarid southern arava valley israel late pleistocene gravelly and sandy wadi deposits associated with fault related colluvial sediments were exposed in trench 17 t 17 which was excavated across a distinct fault scarp deposition of the lower alluvial beds in t 17 took place between 90 and 100 ka this was followed by the first period of tectonic activity and by erosion the age of the upper alluvial bed ranges from 75 to 60 ka a period of stability and reg soil formation was then followed by two scarp forming faulting events resulting in colluviation the colluvium deposited after the second event was dated to 36 ka modern colluvial sediments from nahal shehoret have residual irsl ages of a few hundred years whereas modem alluvial sediments have ages of a few thousand years colluvial sediments may therefore be more suitable for luminescence dating in arid regions

accumulation and intense bioturbation of bioclastic muds along a carbonate platform margin dry tortugas florida abstract a sedimentological study was undertaken in the dry tortugas lowermost florida keys to examine processes influencing the accumulation and sedimentary fabric characteristics of carbonate muds along the shallow margin of a carbonate platform sedimentological studies physical properties 234th and 210pb geochronology were coordinated with observations of benthic biology and benthic boundary layer dynamics sampling was concentrated around a mud depocenter in southeast channel a reentrant 20 30 m deep in the southern edge of the dry tortugas platform in the depocenter of southeast channel accumulation rates of 0 10 0 32 cm y 1 are estimated from 210pb profiles likely sources of sediment are in shallower water and include reefs and beds of calcareous green algae fine sediment silt and clay sized is advected to the seabed of southeast channel by a combination of tidal and storm driven currents flows from shallow water decelerate upon entering deeper water in southeast channel producing conditions favorable to long term accumulation once deposited sediment in southeast channel is subjected to bioturbation by a two tiered benthic community the surface zone 0 5 cm is mixed biodiffusively by a surface community of small bivalves and polychaetes db 9 cm2 yr 1 over periods of weeks to months and is characterized by mm scale mottling other near surface structures include biodeposited fecal mounds of deep deposit feeders and ephemeral physical stratification as thin 1 5 cm layers of fine sediment below 5 cm the dominant post depositional process is bioadvective mixing by a deep deposit feeding community of callianassid shrimp and notomastid polychaetes the upper 10 15 cm is mixed completely every 6 21 years and bioturbation below this depth is slower even though the study area has been hit by 10 major hurricanes in the last 120 years winds 190 km h 1 sediments preserved i e below 5 cm depth in southeast channel during this period reveal wholly biogenic sedimentary fabric produced by the deep callianassid notomastid community bioturbation is thus capable of erasing the stratigraphic signature of the most extreme sediment transport events over decadal time scales

esr dating of fault gouge the effect of grain size abstract esr signals of quartz grains in fault gouge have been partially or completely reset by movements on the fault which allows the dating of the last fault movement in order to better understand the zeroing process we have studied the variation in esr signal ad and age in various grain sizes since it can be expected that larger grains will be less affected by stress than smaller grains we propose that a plateau of constant lower age for the smallest grains indicates total resetting this is confirmed in gouge from a fault in california only such samples should be used for dating

late pleistocene holocene activity and paleoseismicity of the nojima fault in the northern awaji island southwest japan abstract field investigations and analyses of tectonic landforms show that the topographical markers of terrace risers and alluvial fans formed in the late pleistocene holocene have been systematically offset by 40 62 m along the nojima fault on which the 1995 mw 6 9 kobe earthquake occurred analysis of tectonic landforms trench excavations and radiocarbon dating results reveal that i at least two large earthquakes prior to the 1995 mw 6 9 kobe earthquake occurred in the past 1800 years ii the most recent event occurred in 1000 ce and the penultimate large earthquake event took place in 200 ce suggesting an average recurrence interval of 900 yr for large earthquakes on the nojima fault based on the deformation features of tectonic landforms and radiocarbon dating ages the late pleistocene holocene strike slip right lateral rate is estimated to be 2 0 3 0 mm yr with an average of 2 5 mm yr for the nojima fault these findings show that previous studies had significantly overestimated the recurrence interval and underestimated the slip rate of the nojima fault accordingly the nojima fault poses a much greater seismic hazard than previously believed and therefore it is necessary to reassess the potential seismic hazard for the densely populated awaji kobe regions southwest japan