hydrogeomorphic influences on salt marsh sediment accumulation and accretion in two estuaries of the u s mid atlantic coast abstract salt marshes in two contrasting estuaries of the u s mid atlantic coast barnegat bay and delaware bay were investigated to identify relationships between rates of sedimentation and marsh estuarine geomorphic setting barnegat bay is a microtidal lagoon estuary with back barrier and mainland coastal marshes whereas delaware bay is a micro mesotidal coastal plain estuary with sediment rich estuarine marshes salt marshes of both estuaries are dominated by spartina alterniflora an analysis was performed to characterize marsh hypsometry and tidal flooding characteristics and a coring study was conducted to measure rates of mineral sediment accumulation organic matter accumulation and vertical accretion using 137 cs and 210 pb chronology at nine sites in both estuaries mineral sediment and organic matter accumulation rates were significantly higher in delaware bay marshes sediment mean and 1 2 57 2 03 kg m 2 year 1 organic 0 65 0 26 kg m 2 year 1 than in barnegat bay sediment 0 31 0 27 kg m 2 year 1 organic 0 29 0 08 kg m 2 year 1 as were rates of accretion delaware bay 0 79 0 06 cm year 1 barnegat bay 0 28 0 06 cm year 1 regression analysis indicated that marsh accretion rates were positively correlated with rates of sediment and organic accumulation but the upper limit of accretion was governed by sediment accumulation tidal flooding frequency and duration did not correlate with marsh accumulation or accretion rates in either estuary suggesting that hydroperiod is subordinate to sediment availability in governing rates on 50 100 year time scales if true natural and or human influences on suspended sediment production and transport in these estuaries has potential to impact marsh accretionary status and stability independent of sea level rise

late neogene continental stages in nw europe revisited pollen records from fluvial deposits in the netherlands have traditionally been used to establish continental stages for the neogene in nw europe these stages are still widely used across europe for stratigraphic correlations and palaeoclimatic studies despite their extensive use the validity of this continental correlation scheme for the plio and pleistocene has never been tested in the area where they were originally proposed the roer valley graben rvg the fluvial and deltaic depositional setting in this area is controlled by a complex pattern of tectonic and climatic processes which strongly complicates the definition of stages and sub stages of regional or supra regional significance here the original palynological data used to define the praetiglian reuverian brunssumian susterian and linne sub stages are assessed and compared to new borehole data with a multivariate correspondence analysis approach we show that most of these stages cannot be distinguished by numerical analysis of the pollen assemblages a tripartition of pollen assemblages is possible which results in a cooler pleistocene cluster warm temperate to sub tropical pliocene cluster and a warm and relatively dry late miocene to early pliocene cluster however no further stages sub stages or clear climatic phases can be consistently recognized in these data a detailed lithostratigraphic framework of the study area allows a correlation of the sections independent of the pollen data results confirm the numerical analyses and furthermore point to a strong lithological depositional bias on the pollen assemblages variations in the abundance of sequoia and taxodium originally used to define the brunssumian reuverian transition and brunssumian a c sub stages are shown to represent mostly local changes the number and absolute percentage of the fluctuations in sequoia and taxodium abundances depend largely on the sample resolution and the site location within the rvg our data assessment indicates that long distance chronostratigraphic correlations based on the original continental neogene stages likely are invalid furthermore the palaeoclimatic reconstructions that have been based on the rvg successions are largely over interpreted the present palaeoclimate reconstructions from the rvg reflect variations in the highly dynamic fluvial depositional setting taphonomic effects and environmental conditions including climate a sequence stratigraphic approach combined with the analysis of interfingering marine sediments is potentially better suited to establish absolute ages and associated climatic conditions of the neogene deposits within the rvg 2007 elsevier b v all rights reserved

uplift in the nepal himalaya revealed by spirit leveling a 250 km long first order leveling line linking the geodetic surveys of tibet and india through the kingdom of nepal has been measured twice in the past 15 years changes in relative bench mark elevation projected along a 200 km line orthogonal to the mean structural trend in the himalaya indicate a pattern of uplift with wavelengths of 30 50 km not related to earthquake occurrence relative vertical velocities of bench marks of up to 4 mm year show no evident correlation with level line slope an absence of microearthquake data prevents localized uplift from being attributed to slip on mapped or buried faults although circumstantial evidence suggests this is likely in the north in line with the high himalayan peaks relative uplift rates of 4 1 mm yr and a wavelength of 50 km are coincident with a steepening in the main boundary thrust and the moho proposed by lyon caen and molnar 1985 in the south uplift rates of 2 0 3 mm yr with a wavelength of 30 km correspond to active folding of an anticline on the southern flank of the lesser himalaya observed tilt rates of 0 06 rad year are similar to the long term tilt rates needed to produce the 40 70 flanks of the anticline a range of detachment geometries and slip velocities can generate the observed deformation field but geologically realistic models fall into a group of horizontal to shallow dipping sub horizontal faults between 12 and 6 km in depth no unique solution exists although the wavelength of the observed deformation field permits models with significant slip closer than 4 km to the surface to be excluded

long term salt marsh vertical accretion in a tidal bay with reduced sediment supply abstract because of damming and intensive human activities the sediment supply to many estuaries and deltas is dramatically decreasing in the oosterschelde southwest netherlands a storm surge barrier ssb and two compartmentalization dams were built in the 1980s to protect the densely inhabited inland against flooding after these constructions the tidal range and mean high water level in the oosterschelde decreased by about 12 and suspended sediment concentrations in the channels dropped by 52 70 compared to the pre barrier conditions the vertical accretion rates of the three largest salt marshes rattekaai sint annaland and slaak in the oosterschelde in response to this decreased sediment supply were investigated there was a general accreting trend over the entire post barrier period 1988 2011 in all three marshes the predicted slowdown in accretion rates by de jong et al 1994 did not persist although accretion rates were lower than in the pre barrier period more than 20 year observations from kaoline markers showed variation of accretion rates within and among marshes year to year variation in accretion rates was large but only weakly not significantly related to the duration and frequency of marsh overflow and over marsh extreme flooding events however storm events are hypothesized to be responsible for the observed trends but our observations lack the temporal resolution to identify specific storm events salt marshes in the oosterschelde are expected to survive under the present sea level rise rate and subsidence rate scenarios

late pleistocene and holocene large magnitude earthquakes along himalayan frontal thrust in the central seismic gap in nw himalaya kala amb india abstract the himalayan frontal thrust hft forms the southernmost active tectonic mountain front of the himalaya to understand the ongoing tectonics further paleoseismological study has been carried out in the vicinity of the hft system along the himalayan front near kala amb india the trench excavation survey conducted across an explicit surface exposure of the hft exhibits two distinct faults considered to be associated with the reactivation of the hft where the middle siwalik rocks late miocene have repeatedly thrust over the late pleistocene and holocene sediments presence of large sized coseismically induced sand injection feature and its disposition recognized in the trench also suggest occurrence of large magnitude earthquakes in this region an uplifted and upwarped strath terrace 3 to 5 m thick alluvium resting over the 15 m high middle siwaliks abruptly truncated by the hft indicates its latest activity optically stimulated luminescence dating techniques were employed to constrain the chronology of events the long term slip rate of the abandoned terraces due to the activity of the hft is estimated to be 3 4 mm yr or greater since late holocene the paleoseismological investigations have provided unambiguous evidences of at least two large magnitude earthquakes occurred in this region where an earthquake with 12 m or larger surface displacement and magnitude 7 5 or greater hit this region in the period between 29 3 ka and 17 ka in the late pleistocene and another great earthquake recurred with 20 22 m or more surface displacement and magnitude of 7 7 or greater between 5 8 ka and 2 ka in the holocene the present study is the first time report of multiple large magnitude paleoearthquakes in the northwestern part of the frontal himalaya during late pleistocene and holocene the repeated reactivation of hft substantiates high seismic potential of the frontal himalaya and calls for more extensive study of paleoearthquakes of this vastly populous mountainous region

solutions in chronostratigraphy the paleocene eocene boundary debate and aubry vs hedberg on chronostratigraphic principles abstract in several recent papers m p aubry et al have argued that hedbergian principles of chronostratigraphy are being violated by the international commission on stratigraphy ics when selecting global stratotype sections and points gssps for the formal divisions of the geological time scale the current debate over the definition of the paleocene eocene p e boundary has been a major focus of their arguments unfortunately aubry et al have obscured matters by misusing the term unit stratotype and by equivocally using the term stage for the very different concepts of synthem and global chronostratigraphic stage the p e boundary option most repugnant to aubry et al carbon isotope excursion cie p e thanetian ypresian boundary is perfectly compatible with h d hedberg s views in contrast another option preferred by aubry et al recognition of new 1 m y duration age stage between thanetian and ypresian is inconsistent with hedberg s views additional problems with the p e boundary arguments of aubry et al include the fact that a ypresian unit stratotype does not exist the fact that the base of the ypresian synthem is not immutable and the fact that the nannofossil tribrachiatus digitalis is of dubious relevance to the boundary debate as for chronostratigraphy in general aubry et al have misrepresented hedberg s views by 1 falsely claiming that the content of a stage is what determines its boundaries 2 misunderstanding the general concept of the boundary stratotype 3 distorting the base defines boundary principle 4 falsely claiming that traditional pre gssp chronostratigraphic boundaries cannot be changed 5 falsely implying that traditional stage unit stratotype boundaries can be adjusted by no more than 300 000 years when defining formal age stage boundaries with gssps 6 falsely claiming that the definition of a geochronologic chronostratigraphic boundary should precede its correlation 7 claiming that traditional unconformable stage boundaries may be suitable horizons for gssps 8 distorting the meaning of arbitrariness in regard to the definition of geochronologic chronostratigraphic boundaries and 9 claiming that gssps are inherently unstable in that they are subject to redefinition whenever a more powerful element of correlation is discovered if taken seriously the unit stratotype sanctifying chronostratigraphic philosophy of aubry et al would require the creation of perhaps dozens of new phanerozoic ages stages of relatively very short duration wherever there was a significant gap between two successive historical stage unit stratotypes for all of these reasons the arguments of aubry et al have no merit

magnetostratigraphic calibration of the european neogene mammal chronology abstract this paper presents first a discussion on the status of the subdivisions of the european neogene mammal chronology and second it synthesizes all available magnetostratigraphic data from europe to provide chronological framework for mammal localities mammalian events and mammalian biochronologic units of the european neogene because of the lack of their rock equivalents the subdivisions of the european neogene based on mammals have not attained the stage status in terms of reliability except the vallesian and turolian therefore they are designated as the european land mammal ages elma magnetostratigraphic data on mammal bearing deposits in europe is still scarce in time and space consequently it is not yet possible to correlate accurately all elma and mn zones with the geomagnetic polarity time scale gpts nevertheless several studies dealing with mammal localities and their deposits around the oligocene miocene boundary in the middle and late miocene provide reliable correlations of some elma and mn zone boundaries thus the calibration of the oligocene miocene boundary at the base of chron c6cn 2n is in agreement with its age in marine deposits the well known hipparion datum astaracian vallesian boundary is now dated as about 10 8 ma occurring slightly above the base of chron c5n 2n this paper also reviews magnetostratigraphic correlations of some late miocene and pliocene mammal localities in the paratethys area taking into account the chronological assessments in other parts of europe for some key mammalian events new correlations with the gpts have been proposed for these localities thus some new ages are suggested for the late miocene and pliocene paratethys stages

revisiting the earthquake sources in the himalaya perspectives on past seismicity abstract the 2500 km long himalaya plate boundary experienced three great earthquakes during the past century but none of them generated any surface rupture the segments between the 1905 1934 and the 1897 1950 sources known as the central and assam seismic gaps respectively have long been considered holding potential for future great earthquakes this paper addresses two issues concerning earthquakes along the himalaya plate boundary one the absence of surface rupture associated with the great earthquakes vis a vis the purported large slip observed from paleoseismological investigations and two the current understanding of the status of the seismic gaps in the central himalaya and assam in view of the paleoseismological and historical data being gathered we suggest that the ruptures of earthquakes nucleating on the basal detachment are likely to be restricted by the crustal ramps and thus generate no surface ruptures whereas those originating on the faults within the wedges promote upward propagation of rupture and displacement as observed during the 2005 kashmir earthquake that showed a peak offset of 7 m the occasional reactivation of these thrust systems within the duplex zone may also be responsible for the observed temporal and spatial clustering of earthquakes in the himalaya observations presented in this paper suggest that the last major earthquake in the central himalaya occurred during ad 1119 1292 rather than in 1505 as suggested in some previous studies and thus the gap in the plate boundary events is real as for the northwestern himalaya seismically generated sedimentary features identified in the 1950 source region are generally younger than ad 1400 and evidence for older events is sketchy the 1897 shillong earthquake is not a decollement event and its predecessor is probably 1000 years old compared to the central himalaya the assam gap is a corridor of low seismicity between two tectonically independent seismogenic source zones that cannot be considered as a seismic gap in the conventional sense

a rupture model for the great earthquake of 1897 northeast india we assume that the unusually deep extensive and long lasting floods of 1897 along the section of the brahmaputra river north of the western shillong plateau were due to local ground subsidence associated with the great earthquake which occurred on june 12 of that year in the western part of northeast india numerical simulations of ground level changes due to slip on a buried low angle thrust fault dipping due north then show that the northern limit of the rupture zone of this earthquake should have been along the e w flowing brahmaputra river about 40 km north of the northern edge of the shillong plateau and about 70 km south of the himalayan mountain front a similar interpretation of a ground tilt observation suggests that the western limit of the 1897 rupture zone was along the western margin of the shillong plateau the e w and n s dimensions of the rupture zone are estimated to be 170 km and 100 km respectively so that it enclosed the western half of the shillong plateau and areas north of it up to the brahmaputra river the rupture depth could not be estimated from the available data on ground level changes and was constrained at 15 km beneath the southern margin of the shillong plateau on other evidence the above thrust fault should be of the nature of a detachment at midcrustal depth which arose because the continental crust associated with the indian shield terrains of the shillong plateau and mikir hills immediately to the east could not subduct under the continental crust of the eurasian plate to the north and east it is tentatively suggested that although this detachment may extend under the himalaya it may not be the detachment on which the great earthquakes of 1905 1934 and 1950 have occurred in the northwestern central and eastern himalaya respectively it is also suggested that a distinction should be made between the seismicity of the himalaya and the seismicity of the himalayan convergent plate margin hcpm an earthquake of the himalayan seismic belt is also an earthquake of the hcpm but the converse need not hold true since the inferred northern limit of the 1897 rupture zone is about 70 km south of the himalayan mountain front it is suggested that this earthquake belongs to the hcpm but not to the himalayan seismic belt thus conservatively a seismic gap of about 700 km may exist along the himalayan seismic belt between the eastern and western limits of the ruptures zones of the great 1934 and 1950 earthquakes respectively

correlation and geochronology of middle eocene strata from the western united states abstract in this study i integrate marine and continental biostratigraphy magnetic polarity stratigraphy and radioisotopic chronology in a synthetic correlation of middle eocene strata from the western united states more than 2000 m of section were sampled from volcaniclastic deposits aycross and tepee trail formations northwestern wyoming lacustrine and fluviatile deposits washakie formation southwestern wyoming and intertonguing marine and continental strata la jolla and poway groups san diego area california detailed demagnetization studies on numerous pilot samples from all three field areas revealed moderately complex magnetizations most sample nrm s are dominated by a strong normal polarity magnetic component alternating field demagnetization does not consistently isolate the primary magnetization high blocking temperature hematite is frequently a significant carrier of remanence therefore most samples were subjected to detailed stepwise alternating field and thermal demagnetization to 600 650 c the east fork basin area northwestern wyoming magnetic polarity sequence consists of five major polarity intervals a to e the thick washakie formation sequence contains four a to d and the san diego area sequence has four polarity intervals a to d a new biochronologic interval the shoshonian land mammal subage earliest uintan is defined and characterized in all three field areas shoshonian earliest uintan faunas and the bridgerian uintan boundary occur within a single long reversed polarity interval correlation of marine biostratigraphy between the san diego area section and deep sea sections allows precise identification of san diego polarity interval b as chron c21n therefore the bridgerian uintan boundary and earliest uintan faunas occur within the reversed interval of chron c20r high temperature k ar dates bracketing this horizon in northwestern wyoming provide an age estimate of approximately 49 5 ma for the top of chron c21n and 49 ma for the bridgerian uintan boundary berggren et al 1985 use the age estimate of 49 5 ma for the top of anomaly 21 younger boundary of chron c21n as one calibration point for the generation of a paleogene geochronology the methodology and conclusions of this geochronology are compared to those of other recent geochronologies data from independent studies integrating high temperature radioisotopic dates biochronology and magnetochronology are used to test the validity of the berggren et al 1985 geochronology

integrated biomagnetostratigraphy of the alano section ne italy a proposal for defining the middle late eocene boundary the alano section has been presented at the international subcommission on paleogene stratigraphy isps as a potential candidate for defi ning the global boundary stratotype section and point gssp of the late eocene priabonian stage the section is located in the venetian southern alps of the veneto region ne italy which is the type area of the priabonian being exposed along the banks of the calcino torrent near the village of alano di piave it consists of 120 130 m of bathyal gray marls interrupted in the lower part by an 8 m thick package of laminated dark to black marlstones intercalated in the section there are eight prominent marker beds six of which are crystal tuff layers whereas the other two are bioclastic rudites these distinctive layers are useful for regional correlation and for an easy recognition of the various intervals of the section the section is easily accessible crops out continuously is unaffected by any structural deformation is rich in calcareous plankton and contains an expanded record of the critical interval for defi ning the gssp of the priabonian in order to further check the stratigraphic completeness of the section and constrain in time the critical interval for defi ning the priabonian stage we performed a high resolution study of integrated calcareous plankton biostratigraphy and a detailed magnetostratigraphic analysis here we present the results of these studies to open a discussion on the criteria for driving the golden spike that should define the middle eocene late eocene boundary

the pliocene and quaternary fluvial archives of the rhine system abstract the river rhine is one of the few major fluvial systems that connect the areas of the alpine glaciers and scandinavian ice sheet and so provides a key for correlating the two glacial areas in northern and middle europe the fluvial sequences of the rhine valley include at least 11 pleistocene terraces in the lower rhine area 2 pliocene and 12 pleistocene terraces in the middle rhine area resulting in 15 different pliocene and pleistocene terraces based on the correlation between lower and middle rhine the formation of fluvial terraces is significantly influenced by climatic and tectonic processes the terrace staircases are a result of uplift in the middle rhine area and the southern part of the lower rhine area whereas subsidence in the northern part of the lower rhine area resulted in buried stacked sequences magnetostratigraphic data provide chronological constraints for the terrace deposits in the lower rhine embayment and middle rhine region the matuyama brunhes boundary is a reliable marker horizon for the upper terrace fluvial deposits exposed in the karlich clay pit in the middle rhine area the first appearance of volcanic heavy mineral grains in the terrace sediments in loess and soils can be correlated from the middle rhine area through the lower rhine embayment to the netherlands the first occurrence of nordic components in terrace sediments of the lower rhine area is known from gravel on top of the kempen krefeld beds and so are younger than the holsteinian but older than the penultimate glaciation in the lower middle rhine area 40ar 39ar dating of tephra layers intercalated in the aeolian and fluvial sediments provide age constraints the upper pleistocene aeolian sediments overlying the terrace deposits have been dated by luminescence methods and the tephra from the laacher see eruption 12 860 bp is present in the younger lower terrace deposits

salt marsh accretion and sea level movement in the inner severn estuary southwest britain the archaeological and historical contribution the sea defences of the inner severn estuary may be dated partly by reference to historical sources and partly by the detection through field walking of early settlements on the reclaimed wetlands largely as the result of an intensive programme of levelling from reclaimed to active tidal marshes across dated defences it is shown that relative sea level c mean high water spring tides has risen in the area by at least 1 3 m since the later roman period the rise since c 1945 is given by a geochemical method which exploits the presence of metal pollutants in the deposits of the active marshes a marked acceleration in the upward movement of the relative level is suggested by the assembled data the minimum average rate of rise is apparently 0 40 mm a 1 between the later roman period and the medieval period 0 79 mm a 1 from then to the start of the modern period 1 49 mm a 1 through the modern period to c 1945 and 4 65 mm a 1 since c 1945 depending on the extent to which the severn estuary has experienced marine transgression over the period covered by the measurements the relative rise of mean high water spring tide level to the present could amount to about 1 75 m

role of static stress transfer in earthquake occurrence in the himalaya abstract coulomb failure hypothesis suggests that earthquake interaction can lead to earthquake sequences and clustering this implies that the phenomenon should be considered a fundamental feature in any description of seismicity and evaluation of the seismic hazard and risk of a region we translate this idea to the himalaya and investigate how significantly the past earthquakes of the region may have influenced the present day seismicity and seismic hazard potential along its different segments for this we estimate separately the change in coulomb failure stress at the source of the most recent moderate magnitude earthquake along the kumaon garhwal segment the march 29 1999 chamoli earthquake due to two possible major sources these are i the process of subduction of the indian plate beneath the himalaya and ii some selected preceding moderate and small earthquakes in and around the region during their post seismic phase our results indicate that the change due to the former source completely overshadows that due to the latter the implication of our calculations is that the plate subduction processes in the himalaya i actively promote large moderate and small earthquake activity and ii also indirectly influence the regional seismicity through the occurrence of the past earthquakes

on interseismic elevation changes observed near 75 5 e longitude in the nw himalaya abstract we interpret in this article the available observations of interseismic elevation changes along the pathankot dalhousie leveling line near 75 5 e longitude in the nw himalaya we find the data consistent with the view that the major earthquakes of this section of the himalayan convergent plate margin may occur in a manner similar to that inferred for subduction zones along the pacific rim in both cases the main thrust zone mtz a dipwise section of the plate boundary fault pbf which ruptures during major earthquakes is locked in the interseismic period and the overlying rocks experience downdip drag due to subduction of underlying rocks at the local plate convergence rate we estimate that the mtz may have a downdip width of only 25 km in the vicinity of the leveling line we estimate also that in the current interseismic period enough strain may have accumulated already for the next major earthquake of the region

long term accretion rates on tidal salt marshes abstract long term variations in salt marsh accretion rates were estimated using data collected on the marshes of the north norfolk coast england fourteen discrete marsh areas were sampled all lying within a 20 km stretch of coast the age of each marsh had previously been determined using radiocarbon or archival evidence for the date of vegetation inception on each marsh surface marsh ages ranged from 10 years to 2000 years the elevation of each marsh surface was determined in the field using levelling techniques the relationship between age and surface elevation was assumed to be a function of the rate of marsh accretion within this area of coast statistical tests showed this to be a highly significant relationship while the accretion rates calculated from the age height curve agree closely with field measurements on these marshes accretion rates were found to vary from 1 7 cm yr on 10 year old marshes to less than 0 002 cm on marshes older than 500 years the age height relationship describes an asymptotic curve with the asymptote lying 0 8 m below the level of the highest spring tides and appears to be controlled by the frequency of tidal maxima which peaks at 0 8 m below the maximum value and declines sharply above that height

constraints on the structure of the himalaya from an analysis of gravity anomalies and a flexural model of the lithosphere the intracontinental subduction of india beneath the himalaya presents several similarities to that occurring at island arcs we study one of those similarities by analyzing gravity anomalies across the himalaya assuming that the topography is supported by the indian elastic plate flexed under the weight of both the overthrust mountains and the sediments in the ganga basin we first examine in detail the effects of each of the following parameters on the configuration of the elastic plate and on the gravity anomalies the flexural rigidity the position of the northern end of the elastic plate the amount of underthrusting of such a plate beneath the range and the density contrasts between the crust and mantle and between the sediments and the crust a plate with a constant flexural rigidity of about 0 7 1025 n m between 0 2 and 2 0 1025 n m allows a good fit to the data from the lesser himalaya and the ganga basin such a plate however cannot underthrust the entire himalaya instead the gravity anomalies show that the moho steepens from only about 3 beneath the lesser himalaya to about 15 beneath the greater himalaya this implies a smaller flexural rigidity beneath the greater himalaya 0 1 to 1 0 1023 n m than beneath the ganga basin and the lesser himalaya even with a thin weak plate beneath the greater himalaya the weight of the mountains depresses the plate too much unless an additional force or moment is applied to the plate the application of a bending moment unit length to the end of the plate of about 0 6 1018 n m is adequate to elevate the indian plate and to bring the calculated gravity anomalies in agreement with those observed both the smaller flexural rigidity and the bending moment can be understood if we assume that part or all of the indian crust has been detached from the lower lithosphere that underthrusts the greater himalaya we study the tectonic implications of these results by means of a series of idealized balanced cross sections from the collision to the present that reproduce several important features of the geology of the himalaya and predict an amount of eroded material comparable to that in the ganga basin and the bay of bengal these cross sections include high grade metamorphic rocks near the main central thrust and a steeper dip of it there than in the lesser himalaya they predict rapid uplift only in the greater himalaya and at the foot of the lesser himalaya

temporal and spatial variation in intertidal sedimentation rates sediment deposition and erosion rates are reported for an intertidal zone in the burry inlet south wales measured deposition rates over the salt marsh are compared with deposition rates calculated from observed suspended sediment concentrations notably it is concluded that residual turbulence at slack water should not be discounted when calculating deposition rates grain size distributions of suspended sediments over the marsh surface during flood and ebb tides contrast with the grain size distribution of deposited marsh sediments the latter being significantly coarser these data in conjunction with mass budget calculations are used to relate total annual deposition and sediment supply by tidal action during settled meteorological periods the analysis suggests that episodic storm induced sediment transport is probably an important mechanism for introducing coarse sediment on to the marsh surface finally it is noted that seasonal reworking of the sandy non cohesive sediments may be related to variations in the intensity of wave breaking throughout the year

remarks on the palynology based chronostratigraphical subdivision of pliocene terrestrial deposits in nw europe the chronostratigraphical subdivision of the pliocene and early pleistocene as applied in terrestrial deposits of central and nw europe largely relies on the pollen analytical investigations this subdivision is almost entirely based on the interpretation of quantitative changes of the vegetational cover as recorded by the pollen content of fluvial deposits in the lower rhine embayment the early and middle pliocene stages are originally defined in the type areas near susteren and brunssum along the southern border of the roer valley graben rvg late pliocene and early pleistocene stages have been defined in the venlo tegelen area on the peel block just north of the rvg a critical review of existing data has been carried out considering lithostratigraphical data provenance studies and palaeogeography in comparison especially with the interpretation of palynological results as a result it is concluded that the existing subdivision of the pliocene into stages and substages defined by pollen assemblages has not been executed correctly as a consequence the application of this subdivision in geological reconstructions and modelling reveals many problems and pitfalls 2006 elsevier ltd and inqua

stable isotope stratigraphy of the early quaternary of borehole noordwijk southern north sea abstract between 2 58 ma and 2 4 ma most of the present onshore sector of the netherlands was an epicontinental sea previous studies suggest the occurrence of multiple cold and warm phases in shallow marine successions of the maassluis formation in conjunction with the first prominent northern hemisphere ice sheet expansions nevertheless correlation with deep marine isotope stages is tentative and relies on relative dating as absolute dating techniques are difficult to apply here we present for the first time an early quaternary high resolution benthic stable isotope record from the onshore sector of the netherlands taken from borehole noordwijk we tune our record to mis 100 94 using the characteristic 18o signature and complementary biostratigraphic data this new high resolution isotope chronology is providing important insights on stratigraphy and palaeoenvironmental development of the southern north sea area during the early quaternary

seismotectonics of the himalayan collision zone geometry of the underthrusting indian plate beneath the himalaya fault plane solutions and well determined focal depths of medium sized earthquakes topography and landsat imagery in conjunction with seismicity maps cross sections and available geological information are used to investigate the present tectonics of the himalayan continental collision zone most of the accurately located epicenters of events along the himalayan arc 78 e 95 e that occurred between 1961 and 1981 are concentrated in a narrow zone about 50 km wide lying between the northerly dipping main boundary mbt and main central mct thrusts most of these events are located just south of the mct though the epicenters of the events are in general well located their depths as determined by teleseismic travel time data are very unreliable events with accurately determined depths obtained from identification of surface reflected phases define a simple planar zone from about 10 km and 20 km depth with an apparent dip of about 15 this result is all the more remarkable considering that the events used were located along about an 1800 km length of the himalyan arc except for one all available focal mechanisms of events within this zone indicate shallow 30 north dipping thrusts this shallow north dipping zone apparently defines a part of the detachment that separates the underthrusting indian plate from the lesser himalayan crustal block the spatial extent and the geometry of this interplate thrust zone strongly indicate that the mbt and nearby subsidiary surface and blind thrusts rather than the mct are currently the most active structures of the himalayan arc we suggest that the great himalayan earthquakes m 8 occur along the same detachment surface as defined by the thrust type medium sized events events located to the south of the mbt and beneath the ganges foredeep show normal faulting with t axes perpendicular to the himalayan trend the above results suggest that the indian continental plate is underthrusting the himalayan crustal blocks in a relatively coherent and simple geometry and that this geometry is not much different from that observed along oceanic subduction zones the november 19 1980 earthquake that occurred near the mct near 88 5 e shows a predominantly strike slip focal mechanism one of the nodal planes of this mechanism is transverse to the himalayan structural grain and moreover this plane has a trend similar to that of the recently mapped yadong gulu rift in the tethyan himalaya and in southern tibet just northeast of the earthquake we interpret this predominantly left lateral strike slip mechanism to indicate a possible genetic relationship between transverse structural features in the underthrusting indian plate the kishangang basement fault and the upper himalayan blocks and tibet

slow tilt reversal of the lesser himalaya between 1862 and 1992 at 78 e and bounds to the southeast rupture of the 1905 kangra earthquake summary measurements between 1862 and 1992 of a 77 km long spirit levelling line that crosses the main frontal thrust of the himalaya near dehra dun 78 e reveal a slow reversal of tilt in the early part of the last century unperturbed by the destructive 1905 april 4 kangra earthquake 200 km to the northwest the lesser himalaya are inferred to be tilting currently to the northeast at 0 08 rad yr 1 with similar rate but opposite sign to their tilt in 1862 the absence of co seismic deformation near dehra dun in 1905 indicates that the kangra rupture terminated short of dehra dun consistent with a revised ms 7 8 estimate for the size of the kangra earthquake but inconsistent with previous analyses of the levelling data that interpret a large slope dependent systematic error as co seismic slip the reversal in tilt corresponds to a linear northeast down tilt acceleration of 0 0015 0 0004 rad yr 2

sedimentation accretion and subsidence in marshes of barataria basin louisiana1 vertical accretion and sediment accumulation rates were determined from the distribution of 137cs in cores collected from freshwater intermediate brackish and salt marshes in the barataria basin louisiana vertical accretion rates vary from about 1 3 cm yr l in levee areas to 0 7 in backmarshes mineral sediment content of the marsh soil profile decreased with distance from the coast however vertical accretion rates were about equivalent in areas of the same type autochthonous organic matter appears to be an important factor defining the process and rate of vertical accretion especially in the freshwater marshes except in natural levee areas marsh accretion rates are less than subsidence measured by water level data however this alone cannot account for observed land loss patterns in the basin area

the role of the 1999 chamoli earthquake in the formation of ground cracks abstract the moderate magnitude chamoli earthquake that occurred in the garhwal higher himalaya in the early hours of march 29 1999 caused intense damage to the ground and mountain slopes of the alaknanda mandakini river valley and adjoining region a systematic survey of this induced damage was conducted immediately after the earthquake occurred prominent shallow cracks of significant length negligible width and indeterminate vertical extent conspicuously tensile in nature with little or no slip across the crack planes were observed in the ground at several places along the surveyed route these cracks had formed in the dynamic phase of the chamoli earthquake process that is in the period of time during which the earthquake generated seismic waves were passing through the geographic region of interest however we use the theory of earthquake induced static or long time stress changes to visualize such cracks at some selected sites where ground damage was relatively more intense and varied to suggest lower bound estimates of the dynamic stress contributions of the main shock for their formation based on the results of our analysis we conclude that just prior to the earthquake occurrence under the influence of the local ambient stress field the ground at these sites was already near failure in tension to this in its dynamic phase the chamoli earthquake induced stress perturbations having across the planes of the cracks i shear components which were nearly equal and opposite to similar components of the ambient stress field and ii normal tensile components necessary for triggering tensile failure of the ground the 3 or minimum principal stress component of the resultant perturbed failure stress field thus became sufficiently tensile while the transverse stresses became sufficiently insignificant this facilitated formation of major tensile cracks in the ground there our static estimates of the tensile stress changes at the different sites are in essence estimates of the minimal triggering stress perturbations that was provided by the chamoli earthquake in the dynamic state for the formation of the tensile cracks there

seismotectonic perspectives on the himalayan arc and contiguous areas inferences from past and recent earthquakes abstract spread over countries including pakistan india nepal bhutan and china the himalayan mountain chain the most spectacular result of the indo eurasian plate collision is a locus of destructive earthquakes past earthquakes from this region have impacted vast swathes of frontal himalaya and stretches of alluvial plains south of the range front risk from future earthquakes has increased considering the burgeoning population and an ever expanding built environment in the region while considerable ambiguities exist on the locations ruptures and sizes of the earthquakes during the first half of the last millennium 1255 1344 and 1505 ce those during the latter half 1803 and 1833 ce are quite well documented all reported from the central himalayan segment comprising eastern nepal kumaun and garhwal while dormancy prevailed in the central segment in the intervening period the himalayan arc elsewhere witnessed three large great earthquakes in the last century namely 1905 kangra mw 7 8 1934 bihar nepal mw 8 2 and 1950 upper assam mw 8 6 the last one being the largest intra continental earthquake in the recorded history the april 25 gorkha nepal earthquake mw 7 8 located in the central seismic gap terminated the period of low level seismic productivity that followed the 1950 event the himalayan arc and its contiguous regions are now being investigated using various tools including paleoseismology quite understandably the interpretations and tectonic models do not always converge given the diverse quality and type of data the data from variously sized modern day earthquakes sourced in the diverse structural settings of the himalaya provide better constraints on the source properties of the himalayan earthquakes the source complexity and diversity is a striking point of interest for the post 1950 events and at least some of them seem to deviate from the generally accepted model of great ruptures on a shallow dipping detachment a prime example of such anomalies is the 2005 kashmir earthquake mw 7 6 sourced on an out of sequence thrust the sources of the 1991 uttarkashi mw 6 8 1999 chamoli mw 6 6 and the 2015 gorkha nepal mw 7 8 earthquakes all in the central himalayan segment are attributed to the ramp flat on the down dip part of the main himalayan thrust mht in contrast the 2011 sikkim mw 6 9 and the 2016 imphal mw 6 7 earthquakes are intraplate events sourced within the subducting slab source models of modern day earthquakes 1991 2016 discussed in this paper bring out this plurality of mechanisms expected of a complex subduction cum collisional boundary this review presents the status of current seismotectonic understanding of the himalaya from the analyses of significant earthquakes from the past as well as recent events with a focus on the central himalayan segment

seismotectonics of the kangra region northwest himalaya abstract the occurrence of major and moderate earthquakes having thrust and strike slip mechanism along the longitudinal and transverse feature within the same seismogenic zone requires us to study the area in detail to infer the seismotectonics the epicentral distribution of earthquakes 4 0 mb between chamba and sundernagar region shows the high rate of activity either north of chamba i e north of the main central thrust mct or north of dharamsala in between the panjal thrust pt and mct in the dhauladhar range it is however surprising that all the moderate earthquakes that have triggered in the kangra region have either been in the frontal belt along the transverse features or have followed the arcuate belt close to the main boundary thrust mbt the spatio temporal variation of the seismicity from 1973 to 2000 4 0 mb reveals a migration trend between chamba and sundernagar during the seventies and early eighties the seismicity was concentrated in the chamba region and in the late eighties and early nineties the seismicity shifted around dharamsala and later further north in this arcuate tectonic belt of the chamba sundernagar region the foreland region has a characteristic tectonic setting all the fault and fold structures in the oligocene miocene and neogene pliestocene sediments in the foreland region show relative movement in the area of transverse tectonics the surface structures i e thinning and thickening of the sediments are controlled by the basement cofiguration controlled by the subduction process the mbt and the pt are closely spaced and meet each other just northwest of dharamsala the width of the lesser himalaya in the chamba sundernagar region is also much narrower as compared to the region in the east in garhwal kumaun and western nepal this suggests that the convergence is taken up largely by underthrusting of the lesser himalayan formations along the pt the occurrence of a moderate earthquake of magnitude 6 5 in 1978 and the 1986 dharamsala earthquake along the se dipping and sw dipping nodal planes within the ne dipping thrust regime and displacement of the mbt and pt from 4 to 12 km reflects the active involvement of the ne sw trending fault system in controlling the seismic behavior of the kangra region the microearthquake migration in time and space in the chamba sundernagar region also reflects the time differential segmental collision behavior of the basement

assessing the impact of weir construction on recent sedimentation using cesium 137 ten cores were obtained from a marsh developed along mad island slough texas usa upstream of a weir constructed in 1948 the cores were analyzed for cesium 137 to identify time stratigraphic marker horizons and calculate recent sedimentation rates the cesium 137 analysis provided a 1954 marker horizon in nine of the ten cores a second marker horizon present in all ten cores consisted of an abrupt downcore change in lithology from dark organic rich muds to grey organic poor sands this transition was tentatively identified as coinciding with 1948 and the beginning of marsh sedimentation resulting sedimentation rates show that surprisingly little sedimentation has occurred behind the weir averaging only 27 cm in almost 50 years sedimentation rates in the marsh declined from an average of 2 4 cm yr 1 in 1948 1954 to 0 32 cm yr 1 in 1954 1994 a similar trend of declining sedimentation has been documented for adjoining mad island lake suggesting that land use changes in the lake s watershed have reduced the sediment supply in recent decades the results also suggest that the weir is not a very efficient sediment trap in this watershed

a temporal and spatial study of mudflat erosion and deposition sediment elevations were measured on an intertidal mudflat in maine to determine the temporal and spatial changes in sediment volume the winter and spring months were times of greatest sediment change with erosion in winter months followed by rapid accretion in the spring in some months erosion and deposition took place during the same time interval but on different parts of the mudflat the data suggest that areas of erosion quickly become sites of accretion indicating that an equilibrium surface level is being maintained mudflats may strongly influence the adjacent estuary by acting as sediment banks that can periodically lend sediments to the particulate pool offshore we conclude that mudflats should not be thought of as steady accretionary environments but rather as more variable environments that respond to seasonal changes

paleomagnetism geochronology and possible tectonic rotation of the middle miocene barstow formation mojave desert southern california the barstow formation of the central mojave desert in the mud hills consists of 965 m of epiclastic and volcanic sediments deposited in an extensional rift this widespread unit is of importance because its mammalian faunas characterize the barstovian land mammal age previous isotopic ages on interbedded tuffs have been used to calibrate middle miocene time and it was deposited in a tectonically active region volcanic ash samples were collected from the barstow formation for isotopic dating using conventional 40 k 40 ar and 40 ar 39 ar single crystal laser fusion methods multiple analyses on minerals from 5 superposed tuffs yielded the following mean 40 k 40 ar ages rak tuff at 16 3 0 3 m y oreodont tuff at 15 9 0 2 m y dated tuff at 14 8 0 2 m y hemicyon tuff at 14 0 0 1 m y and lapilli tuff at 13 4 0 2 m y similar mean ages were also obtained on the following tuffs using single crystal 40 ar 39 ar laser fusion methods oreodont tuff at 15 9 0 06 m y dated tuff at 14 8 0 06 m y and hemicyon tuff at 14 0 0 09 m y in order to develop a local magnetostratigraphy 272 paleomagnetic sites were collected from 7 important sections within the mud hills saturation isothermal remanence experiments suggested the presence of either hematite or magnetite as carriers of remanence after either stepwise alternating field or thermal demagnetization characteristic directions were usually isolated between 30 and 50 mt or 300 and 500 c positive reversal and fold tests indicate a stable remanence acquired prior to folding there are 21 magnetic polarity zones interpreted from the continuous part of the barstow formation in the study area by using the 5 isotopic ages determined from interbedded tuffs the local composite polarity pattern is correlated to the top of chron c5d through the bottom of c5ab on the magnetic polarity time scale or an age range from 17 6 to 13 4 m y the boundary between hemingfordian and barstovian land mammal ages herein occurs 30 m below the oreodont tuff 15 8 0 2 m y within c5b and is taken at about 16 0 m y ago the barstow formational mean declination is 347 1 inc 47 5 95 6 51 d 7 97 suggesting negligible or possibly slight counterclockwise rotation r 4 1 r 10 5 for this part of the mojave block during the past 18 m y a 40 ar 39 ar mean age of 19 3 0 02 m y for the red tuff which is near the local base of the barstow formation and unconformably underlying our composite section constrains a minimum age for the beginning of local basin filling with principally epiclastic sediments

pliocene and lower pleistocene vegetation and climate changes at the european scale long pollen records and climatostratigraphy the biostratigraphically calibrated long pollen record at dsdp site 380 southwestern black sea displays a high resolution continuous and contrasted evolution of the vegetation in the region for the entire pliocene and lower pleistocene an accurate correlation is established with the reference global oxygen isotopic curve and with the northwestern european climatostratigraphy climatostratigraphic relationships are evident at the latitudinal and longitudinal scale of europe confirming the extensive strength of pollen analysis as a tool for correlations over large distances

the heidelberg basin upper rhine graben germany a unique archive of quaternary sediments in central europe abstract the heidelberg basin in the german part of the northern upper rhine graben hosts one of the thickest successions of plio pleistocene sediments in central europe from reflection seismic surveys and new research boreholes it is known that pleistocene sediments amount to more than 500 m thickness the basin sediments originated both from local source areas i e the highlands along the graben shoulders and from regional source areas i e the alps although temporal hiatuses probably exist the deposits are expected to be more or less complete because this part of the upper rhine graben has undergone continuous subsidence in the past currently the heidelberg basin is under investigation by a scientific drilling project new cored boreholes have been realized at three different locations spaced 15 km from each other this concept provides complementing information and enables a detailed characterization of the predominantly fluvial deposits the project aims to develop a stratigraphic reference profile of the quaternary for this region north of the alps to understand how the sedimentation was controlled by tectonics and past climate change and to derive proxy data of environmental changes the new core material demonstrates that the heidelberg basin would be a possible key location for quaternary stratigraphy in central europe information about pleistocene periods of cold and warm climate is found within this one sediment succession in superposition the temporal resolution of the sediment succession is high due to its mid continental location it links northern and southern europe as well as western and eastern europe based on a detailed analysis of the new drill cores a new lithostratigraphy for the northern part of the upper rhine graben is developed in a first step with the mannheim formation the ludwigshafen formation the viernheim formation and the iffezheim formation four new lithostratigraphic units of the northern upper rhine graben are officially introduced furthermore a new debate about identification of basal quaternary arises from the new research boreholes whereas during the last decades petrological markers were used to define basal quaternary i e the first deposition of alpine sediments or carbonate content this definition fails in the depocentre of the basin several rock physical properties e g the natural gamma radiation and the magnetic susceptibilities reveal significant changes at the basal quaternary the driving forces of these changes have to be studied in more detail in the future

salt marsh stability and patterns of sedimentation across a backbarrier platform abstract long term observations of clay thicknesses from 1949 to 2007 and measurements of the bulk dry density of salt marsh on the backbarrier of skallingen west denmark formed the basis of constructing a space distributed model of salt marsh deposition the deposition potential an empirical constant was measured at 32 locations across the studied salt marsh platform it was found to correlate with two independent variables 1 distance to marsh edge and 2 distance to creeks of 2nd or higher order they explained in combination 71 of the variation the derived algorithms for estimating the salt marsh deposition made it possible to tune in a model in a 4 by 4 m grid covering the studied salt marsh area of app 3 km 2 this was used to describe the general pattern of deposition on the salt marsh platform running the model with a constant sea level revealed that balance between the inner and the outer salt marsh deposition cannot be achieved within a time scale of 1000s of years modeling salt marsh sedimentation under rising sea level scenarios revealed that only one specific sea level rise provides equilibrium for a given location with a higher sea level rise the marsh at the specific location will eventually drown whereas it with a sea level rise below this level will grow towards the top of the rising tidal frame short term scenarios 100 years showed that the skallingen salt marsh will survive a sea level rise of 4 mm yr 1 and become unstable in the inner part with a sea level rise of 6 mm yr 1

seismotectonics of the nepal himalaya from a local seismic network the national seismological network of nepal consists of 17 short period seismic stations operated since 1994 it provides an exceptional view of the microseismic activity over nearly one third of the himalayan arc including the only segment between longitudes 78 e and 85 e that has not produced any m 8 earthquakes over the last century it shows a belt of seismicity that follows approximately the front of the higher himalaya with most of the seismic moment being released at depths between 10 and 20 km this belt of seismicity is interpreted to reflect interseismic stress accumulation in the upper crust associated with creep in the lower crust beneath the higher himalaya the seismic activity is more intense around 82 e in far western nepal and around 87 e in eastern nepal western nepal between 82 5 and 85 e is characterized by a particularly low level of seismic activity we propose that these lateral variations are related to segmentation of the main himalayan thrust fault the major junctions between the different segments would thus lie at about 87 e and 82 e with possibly an intermediate one at about 85 e these junctions seem to coincide with some of the active normal faults in southern tibet lateral variation of seismic activity is also found to correlate with lateral variations of geological structures suggesting that segmentation is a long lived feature we infer four 250 400 km long segments that could produce earthquakes comparable to the m 8 4 bihar nepal earthquake that struck eastern nepal in 1934 assuming the model of the characteristic earthquake the recurrence interval between two such earthquakes on a given segment is between 130 and 260 years

abrupt holocene indian summer monsoon failures a primary response to solar activity knowledge of the millennial abrupt monsoon failures is critical to understanding the related causes here we extracted proxy indices of indian summer monsoon ism intensity during the early to mid holocene from peat deposits at lake xihu in southwestern china there are a series of abrupt millennial scale episodes of ism weakening inferred from the lake xihu records which are generally synchronous with those inferred from other archives over ism areas an important feature is that the ism failures inferred from the lake xihu proxy indices synchronize well with abrupt changes in solar activity we argue that changes in solar activity play a primary role in producing most of these millennial ism failures while some other causes including freshwater outbursts into the north atlantic ocean and changes in sea surface temperatures of the eastern tropical pacific ocean may have also exerted influences on parts of the millennial ism failures

on the interpretation of slow ground deformation precursory to the 1976 friuli earthquake during three years preceding the 1976 friuli earthquake a continuous southward ground tilt was recorded by a tiltmeter placed near tolmezzo 15 km north west of the epicentre of the impending earthquake the cumulative ground tilt amounted to as much as 3 minutes of arc since the tiltmeter was placed in the proximity of an active fault such a tilt can be explained if the fault slipped aseismically on its shallower section during the same three year period aseismic slip on the fault might have been caused by the same mechanism which concentrated stress in the region and eventually produced the 1976 earthquake

southern limits of major earthquake ruptures along the himalaya between longitudes 75 and 90 e the ruptures responsible for major earthquakes along the himalayan convergent plate margin hcpm occur in a strikewise oriented zone of frictional failure and relative slip in a buried detachment along the upper surface of the indian shield rocks subducting under the himalaya the southern limit of the rupture zone is a geotectonic lineament whose geographic location is important in assessing risk due to earthquakes a major part of this article is taken up in arguing that the available macroseismic and instrumental evidence for the 1934 bihar nepal earthquake is consistent with the view that the rupture which caused it occurred in the detachment mostly under the lesser himalaya northward from the vicinity of the surface trace of the main boundary thrust mbt since a similar location has been inferred by others for the 1905 kangra earthquake rupture a basis arises for postulating that over more than half of the length of the hcpm between 75 and 90 e longitudes the ruptures responsible for major earthquakes lie in the detachment with their southern limits geographically similarly close to the surface trace of the mbt this includes the nearly 700 km long seismic gap between the 1905 and 1934 ruptures

hierarchical subdivision of the cenozoic era a venerable solution and a critique of current proposals abstract if tertiary and quaternary are to be formally defined and ranked then only one topology and two ranking options for the major subdivisions of the cenozoic era are consistent with the principles of hierarchical classification these are 1 for the tertiary and quaternary to be ranked as suberas with the paleogene and neogene ranked as periods of the tertiary or 2 for the tertiary and quaternary to be ranked as periods with the paleogene and neogene ranked as subperiods of the tertiary the first option would leave the period rank empty for quaternary time however so the second option is preferred here in neither case is an extension of the neogene to the present permitted if desired however early cenozoic and late cenozoic could be defined as formal unranked chrons with the latter term providing an unambiguous expression for the same concept as the extended neogene attempts to justify an extended neogene by reference to a statement arising from the 1948 international geological congress fail because they are based on a misinterpretation of that statement likewise an appeal to the alleged original meaning of the neogene fails because it is factually superficial and would also have unacceptable consequences if applied as a general principle to the rest of the time scale four arguments against a ranked tertiary and or quaternary involve the status of these names as parts of an obsolete classification the disparity in their durations an analogy between them and the unranked precambrian and their supposed ambiguity these arguments are readily refuted arguments in favor of a ranked tertiary and quaternary include the continuing widespread use of these names their practical relevance for geologic maps and their role in honoring the pioneers of stratigraphy a recent recommendation by the international commission on stratigraphy ics would decouple the beginning of the quaternary from the beginning of the pleistocene have the neogene and pliocene overlap the tertiary quaternary boundary and have the gelasian age belong to both the pliocene and the quaternary these results violate the existing guidelines of the ics this same proposal would also regard the quaternary as a subera within the neogene period the latter being extended to the present however this arrangement violates the most fundamental rule of hierarchical classification in that a unit of superior rank would be included entirely within a unit of inferior rank given these problems the international union of geological sciences iugs must reject the ics recommendation an improved version of the ics proposal with the quaternary ranked as a period and the paleogene and extended neogene ranked as suberas would still prohibit the tertiary from being ranked and would either violate simpson s rule or else require a new name for the traditional concept of the neogene because the classification of the cenozoic advocated here is strictly hierarchical violates none of the existing guidelines of the ics obeys simpson s rule requires no new names allows the tertiary quaternary paleogene and neogene to be formally ranked and has been in general use for more than a century it is to be preferred only two current options for defining the quaternary and pleistocene are valid namely to leave the beginnings of these units where they are now vrica gssp at 1 8 ma or to move both to the piacenzian gelasian boundary monte san nicola gssp at 2 6 ma the latter option is not prohibited by lyell s types of the older pliocene nor after 2008 by the existing guidelines of the ics but if enacted could jeopardize the stability of the rest of the standard global time scale

on the damage caused by the chamoli earthquake of 29 march 1999 abstract the moderate magnitude chamoli earthquake which occurred on 29 march 1999 in the alkananda river valley region of garhwal himalaya caused considerable loss to human life and property from a systematic field survey of the damage conducted for five continuous days immediately after the earthquake the following could be noted i the consequences of the damage are most pronounced near the main central thrust mct ii the maximum damage is between chamoli and the 40 km2 area to the its north and was probably caused by major uplift iii distinct radial cracks accompanied by considerable ground subsidence due to this earthquake could be observed north of the completely devastated village of mawana situated 4 km northwest of chamoli iv the intensity of damage in the meisoseismal zone covering approx 580 km2 area suggests a value of 0 2 g for the ground acceleration

the process of sedimentation on the surface of a salt marsh abstract an unditched salt marsh creek drainage basin holland glade marsh lewes delaware has a sedimentation rate of 0 5 cm year 1 during normal storm free conditions the creek carries negligible amounts of sand and coarse silt of the material in the waters flooding the marsh surface over 80 disappears from the floodwaters within 12 m of the creek about one half of the lost material is theoretically too fine to settle even if flow were not turbulent however sediment found on spartina stems can account for the loss the quantity of suspended sediment that does reach the back marsh during these normal tides is inadequate to maintain the marsh surface against local sea level rise this suspended sediment is also much finer than the deposited sediments additionally remote sections of low marsh sections flooded by only the highest spring tides have 15 30 cm of highly inorganic marsh muds this evidence indicates that normal tidal flooding does not produce sedimentation in holland glade study of the effects of two severe storms of a frequency of once per year suggests that such storms can deposit sufficient sediment to maintain the marsh the actual deposition of fine grained sediments fine silt and clay appears to result primarily from biological trapping rather than from settling in addition this study proposes that the total sedimentation on mature marshes results from a balance between tidal and storm sedimentation storms will control sediment supply and movement on micro and meso tidal marshes and will have less influence on macro tidal marshes

interpretation of observed ground level changes due to the 1905 kangra earthquake northwest himalaya the kangra earthquake of 1905 in the northwest himalaya was the first indian earthquake for which coseismic ground elevation changes were measured through repeat precision levelling the levelling une from saharanpur to mussoorie via dehra dun was situated near the southeastern extremity of the nw se trending meizoseismal area maximum uplift of 14 3 cm was measured at a bench mark in dehra dun some details of the levelling data having been published recently data for eight bench marks were considered for interpretation in this study in principle these are sufficient for us to estimate eight parameters of a rectangular rupture buried in a homogeneous poisson solid but because of some uncertainties regarding the bench mark positions and also the relatively small amounts of uplift measured at the bench marks we have preferred to use the data as a means to check the reasonableness of rupture models proposed on other grounds rather than to propose a new model independently the observed elevation changes are not in accord with the view that the kangra earthquake was caused by a single 100 km long rupture along the shahpur mandi sector of the northwest himalaya however the data can be explained if in addition a second smaller rupture extending on either side of the levelling une near dehra dun is assumed the data can also be explained if the rupture during the earthquake had 1 a length of 280 km parallel to the general strike of the himalaya from around kangra up to a short distance about 10 15 km northwest of the levelling une near dehra dun 2 a breadth of 80 km perpendicular to the strike of the himalaya 3 a northeasterly dip of about 5 and 4 a depth of 10 15 km along its sw edge finally the elevation data rule out any role for the main boundary thrust in the occurrence of the kangra earthquake this major tectonic feature demarcating the geological boundary between the outer and the lesser himalaya thus appears to be unimportant in the current seismotectonics of the region and the subduction of the indian lithospheric plate under the mountains

accretion rates in salt marshes in the eastern scheldt south west netherlands abstract vertical accretion and sediment accumulation rates were determined from the distribution of 137cs in sediment cores from historic documents and from artificial white coloured tracer layers in salt marshes in the eastern scheldt salt marsh accretion is related to the steady rise of the mean high tide in the eastern scheldt during the last few decades mean accretion rates vary from 0 4 0 9 cm year 1 in the st annaland marsh to 1 0 1 5 cm year 1 in the rattekaai marsh sediment accumulation in accreting marshes exceed the loss of sediment by retreat of the marsh cliffs by a factor of 10 20 short term spatial and temporal variations in accretion rates are large spatial variations are associated with levee and backmarsh sites and the density of marsh vegetation temporal variations are mainly related to fluctuations in hydrodynamic conditions the net vertical accretion rate of organic carbon is 0 4 0 1 kg m 2 year 1 approximately half this rate is associated with the current deposit and the other half with net additions from the belowground root biomass a simple model for the root biomass distribution of spartina anglica with depth and the depth dependent fossilization of root biomass in sediments of the rattekaai marsh is presented

historic large earthquake induced soft sediment deformation features in the sub himalayan doon valley well preserved soft sediment deformation structures were observed at six sites along the course of the baldi nadi in the doon valley of the garhwal himalaya these deformed structures lie in mid and side channel bars of the braided baldi stream the deformed sediments are composed of unconsolidated alternations of mud silt and very fine sand with ripple lamination deformation is restricted to a single stratigraphic layer bounded by undeformed beds suggesting synsedimentary deformation these features can be traced laterally along the course of the braided baldi nadi over a distance of 7 km in isolated bar deposits at one stratigraphic level 1 5 2 m above the lean season water level the deformed features display over steepening of sedimentary strata folding graben type faulting plume like intrusion flame structure slumping related to disrupted bedding and pear drop structure the style and type of deformation vary considerably in the different segments within a single bed while the intensity may be same at one site the deformation features of the baldi nadi are interpreted to be the product of liquefaction and fluidization of unconsolidated mud and silt during historic earthquake s related to the past seismic activity of the main boundary thrust mbt and the himalayan frontal fault hff or blind thrust the intensity of deformation provides an opportunity to reconstruct the felt area magnitude of large historic earthquake s and helps in tracing the palaeoearthquake epicentre the observed earthquake induced soft sediment deformation features indicate that in addition to the 1905 great earthquake the doon valley was also affected by historic earthquake s of magnitude similar 7 possibly corresponding to those of 1803 and or 1720 if not older

tectonic stress field in the indian subcontinent a map of maximum horizontal compressive stress orientation in the indian subcontinent has been prepared using orientations derived from three different stress indicators borehole elongation breakouts in situ hydraulic fracturing measurements and earthquake focal mechanisms most part of the subcontinent appears to be characterized by a compressional stress regime thrust and strikeslip faulting imposed by plate boundary forces although shmax orientations do not in general show clear correlation with the direction of motion of the indian plate four provinces are recognized on the basis of regionally consistent orientations these are the midcontinent stress province the southern shield the bengal basin and the assam wedge their boundaries have been determined taking into consideration regional tectonics and seismicity central and northern india including the shillong plateau stretching up to the great himalaya pakistan and nepal are included in a broad midcontinent stress province characterized by nne ene oriented shmax the mean orientation of shmax in this province is n23 e subparallel to the direction of compression expected to arise from the net resistive forces at the himalayan collision zone suggesting that it is largely determined by the tectonic collision processes much of southern india mysore plateau and the high grade metamorphic terrain south of the plateau appears to be part of a second stress province characterized by nw oriented shmax these appear close to those of the intraplate stress field prevailing in the central indian ocean a third stress province was recognized in the bengal basin including parts of west bengal tripura manipur and mizoram in northeastern india and most of bangladesh this province extends eastward from the marginal fault in the western margin of the bengal basin to the indo burma subduction zone and is bounded on the north by the e w striking dauki fault shmax within the sedimentary pile of the bengal basin is oriented in e w direction while p axes of earthquakes within the basement and the crust beneath the basin and within the subducted slab of the indian plate beneath the indo burman ranges generally trend north n30 e shmax orientations within the sedimentary pile of the basin are parallel to the local approximately e w direction of the convergence of indian and burmese plates suggesting a casual relation to the resistive forces at the subduction zone in the indo burma region interestingly the stress field in the basement and the crust beneath the bengal basin and in the subducted slab is similar to the one prevailing in the midcontinent stress province assam wedge stress region occupies the northeastern corner of the indian plate including upper assam arunachal pradesh and much of nagaland this region subducts beneath a sharply bent continental collision boundary consisting of the northeastern limb of the himalayan and northern limb of the indo burman fold belts as a result the stress field in this province is depth differentiated and most likely responsible for the absence of consistent shmax directions

notes on geochronologic and chronostratigraphic units there is no need to regard the term geochronology as a redundant synonym of either geologic time scale or radiometric dating this term may reasonably be used in reference to all principles and methods employed in geology to determine the relative and numerical ages of all kinds of rocks the term chronostratigraphy would best be restricted to the process of defining the formal subdivisions of the geologic time scale geochronologic unit is best used as a general category term it includes aurichronologic units spans of time defined operationally by golden spikes geochronometric units spans of time defined theoretically in terms of absolute numerical age before present and biochronologic units spans of time defined theoretically by paleobiological events a chronostratigraphic unit is a set of material existing stratified rock that was formed during a given span of time geochronologic unit therefore a geochronologic unit must be defined before the corresponding chronostratigraphic unit can even be conceptualized chronostratigraphic units are generally not isochronous bodies of rock because owing to the unconformities that exist over any appreciable geographic area their upper and lower material boundaries are not everywhere synchronous thus particular systems series and stages are material stratigraphic units of geographically variable time value within the maximum temporal limits of the corresponding periods epochs and ages geochronologic boundaries that have been formally ratified serve a conventional function and will rarely if ever need to be redefined we can continue to discover and debate important events in earth history without insisting that such events must be used to constantly redefine the boundaries of our global temporal pigeonholes

contemporary tectonics of the himalayan frontal fault system folds blind thrusts and the 1905 kangra earthquake the sub himalayan fold thrust belt consists of deformed late cenozoic and older deposits south of the main boundary thrust mbt in pakistan east of the indus river the sub himalaya comprises the potwar plateau and the salt range which is thrust southward over the jhelum river floodplain along the salt range thrust although an estimated 9 14 mm a 1 shortening has been taken up on the salt range thrust during the last 2 ma the range front scarp does not show signs of recent faulting shortening may be shifting southward to the lilla overpressured anticline which rises from the jhelum floodplain as a fault propagation fold farther east shortening is partitioned among several anticlines underlain by foreland and hinterland dipping blind thrusts southeast of the main deformation zone the pabbi hills overpressured anticline is best explained as a fault propagation fold throughout the potwar plateau and salt range thrusts and folds rise from a basal decollement horizon in eocambrian evaporites the pakistani part of the decollement horizon could generate large earthquakes only if these evaporites die out northward at seismogenic depths in india and nepal the sub himalaya is narrower reflecting the absence of evaporites and a steeper slope of the basement towards the hinterland the southern boundary of the sub himalaya is the himalayan front fault discontinuous because part of the shortening is expressed at the surface by folding broad alluvial synclinal valleys dun valleys are bounded on the south by rising barrier anticlines of siwalik molasse the 1905 kangra earthquake m8 produced uplift on the mohand anticline and the dehra dun valley suggesting that this earthquake occurred on a decollement horizon above basement downdip from the fold if so the kangra event is the largest known earthquake on a blind thrust expressed at the surface as a fold

large scale textural patterns and sedimentary processes on tidal salt marshes in the severn estuary southwest britain abstract approximately 840 km2 of largely reclaimed estuarine alluvium border the severn estuary and inner bristol channel today using a direct measure of grain size and the proxy evidence of sediment controlled early land use medieval early modern it is shown that the grain size of the tidal mud deposited on the marshes prior to reclamation declined outward from the main and larger tidal channels toward the bedrock limit of the alluvium variations in the altitude of the marsh surfaces as they survive after reclamation suggest that the deposition rate of this sediment also decreased outward from these sources at elmore a representative narrow ca 1 km marsh grain size change is steep and well defined in contrast at hill in a representative sector from a large and broad ca 5 km marsh the measured change is gradual and disorderly and disturbed by an extensive arcuate belt of relatively coarse sediments based on a review of processes and sedimentation and appealing to a broad geomorphological and hydraulic analogy between tidal wetlands and river floodplains it is suggested that marshes of the elmore type may be supplied with sediment largely by transverse diffusion from the tidal channel whereas hill type marshes may receive considerable mud by convection as well as diffusion

problems in chronostratigraphy stages series unit and boundary stratotypes global stratotype section and point and tarnished golden spikes abstract stratigraphy is a magnificent subject magnificent in its breadth and scope magnificent in its importance to so many lines of human endeavor it is essentially that branch of geology which deals with the arrangement the distribution and the chronological succession of rock strata and other associated rock bodies with respect to any or all of the various characters properties and attributes which rocks may possess hedberg 1958 p 1881 chronostratigraphy the temporal ordering of geologic strata is at the heart of earth history in reviewing chronostratigraphic theory from d orbigny to hedberg we see that concepts and practices have evolved under pressure of constant improvements in time control and data quality such stimuli are naturally felt more strongly in the youngest part of the stratigraphic record where dating is most precise and the biostratigraphic data are most abundant and well preserved it is not surprising therefore to find that chronostratigraphy is conceptually more advanced in the cenozoic erathem than in the mesozoic and paleozoic erathems where biostratigraphy and chronostratigraphy are widely confused evidently out of necessity taking the five inter series boundaries in the cenozoic erathem as case histories we review their current status in relation to the lower boundary of the lowest standard stage above the boundary in light of the hierarchical principle recommended in the international stratigraphic guide hedberg 1976 salvador 1994 in each instance what should be a simple nested relationship turns out to be complex and difficult and in the cases of the proposed global stratotype section and point gssps for the eocene oligocene series boundary and the paleocene eocene series boundary there are discrepancies so large with regard to the base of the rupelian and ypresian standard stages respectively that some essential relaxation of the hierarchic rule seems to be required if the historic value of these long known stages is not to be violated since stage boundaries should not be defined a posteriori to fit series boundaries we propose here to reconsider the role of the standard stage as the obligate elemental subdivision in a rigidly hierarchical chronostratigraphic scale and suggest that series and subseries should be formalized and their boundaries defined by gssps we do not suggest that stages be abandoned on the contrary we propose to integrate them in a two step hierarchical chronostratigraphic framework so as to use them in complementary fashion with series and subseries however the boundary concept is more appropriate for stage than the gssp we recognize the need for precise and globally valid chronostratigraphic correlations based on gssps in attempts to understand the earth system while at the same time we emphasize the need for conceptual continuity with regard to the central place that the stage has played in chronostratigraphy over several decades

on autochthonous organic production and its implication for the consolidation of temperate salt marshes abstract the organic production related to minerogene salt marsh deposits represents a challenge to all attempts to model the development of these areas and evaluate their chances of survival under different sea level scenarios salt marsh deposits on a typical temperate backbarrier saltmarsh area at the skallingen barrierspit denmark were investigated for autochthonous or below ground organic production which was found to have a mean value of 0 14 kg m 2 y 1 or about 0 1 mm y 1 this production is concentrated in the upper approximately 5 cm of the salt marsh below this level the organic material decomposes with a decreasing organic content until about 15 cm below the surface hereunder the decomposition of organic material seems to stabilize at a very low level the constant rate of the below ground organic production results in a larger concentration of this type of organic matter in the slowest accreting salt marsh deposits the root activity is the primary reason for differences in the bulk dry density of salt marsh surface layers therefore the surface layers of slowly accreting salt marshes have the lowest bulk dry density during autocompaction the bulk dry density increases down core this process is only to a small degree

the role of stratotypes in stratigraphy part 3 the wood committee the berkeley school of north american mammalian stratigraphic paleontology and the status of provincial golden spikes abstract the north american land mammal ages defined in 1941 by the wood committee provide good examples of the use of strict nominal stratotypes in fixing the names and establishing the minimum durations of provincial biochronologic units the lithostratigraphic type sections of each age served a name bearing and exemplary function not a boundary defining function despite some inconsistencies in their work the common charge that the wood committee defined many of their ages as lithochrons is a myth nevertheless the potential or actual temporal overlap of some of the original nominal stratotypes of the ages is a significant problem and their redefinition is permissible in order to preserve the original intentions of the wood committee the berkeley school of north american mammalian stratigraphic paleontology has been the most influential force in theoretical discussions in this field since the 1960s d e savage retained most of the oppelian views of r m kleinpell while m o woodburne and d r prothero departed from that tradition and adopted some of the views of h d hedberg and w a berggren thus emphasizing single taxon definitions datum planes and boundary stratotype definitions for stages however recommendations by members of the berkeley school that we turn our land mammal ages into formal stages are ironic because their own writings show they still hold the anti hedbergian view that stages are flexible biostratigraphic biochronostratigraphic entities nevertheless in partial agreement with at least some members of the berkeley school the transformation of our provincial biochronologic units into golden spike defined ages stages would defeat their purpose which is to summarize our evolving knowledge of the true sequence of important paleobiological events in each major fossil group that occurred in a given province in principle and in practice hedberg s attempt to restrict the terms age stage to golden spike defined entities has failed however hedbergians and traditional stratigraphic paleontologists can find common ground if they will admit that aurichronologic and biochronologic units are both legitimate subcategories of geochronologic units if so hedberg s major program would be vindicated in that golden spikes would still be used to define the phanerozoic standard global geochronologic units while traditional stratigraphic paleontologists would retain the ability to modify the boundaries of their provincial ages stages as they saw fit provided that such modifications did not violate the strict nominal stratotypes of those ages stages

landslide hazard mapping based on geological attributes abstract a landslide susceptibility zoning technique is proposed and has been tested in a catchment area of 317 km 2 along the aglar river a tributary of the river yamuna in the himalayas the aglar catchment is characterised by varied rock types mostly sedimentary an active fault landslides moderate to intense seismic activity and moderate human influence very little is known about this terrain except for one previous study this study focusses on the relationship between the terrain parameters and landslide hazard mapping a landslide susceptibility map is presented which can serve as first generation map on which subsequent detailed information can be incorported it is the first map of this kind from the himalayas based on quantitative evaluation of geomorphological and geological parameters on a classified terrain database map the study is in two stages first the terrain has been classified into several homogeneous patterns followed by small physiographic units which are uniform in their characteristics throughout second each unit acquires a score from a rating system based on the degree of mutual relationship between landslides and geological attributes such as slope distance from fault relief dip slope relationship etc each of which has been given weighting according to the strength of this relationship the aim is to frame a practical database system rationally which can be imported into a geographical information system for rapid digital handling of the data a positive relationship established between landslide and sediment yield indicates that long term sediment production in the catchment area comes from the ongoing geological and geomorphological activity the work may have applications in various parts of the himalayas especially the ungauged and unknown catchments falling in similar geological areas and latitudes

tidal marsh sedimentation and resilience to environmental change exploratory modelling of tidal sea level and sediment supply forcing in predominantly allochthonous systems abstract the existence and function of tidally dominated and predominantly allochthonous marshes are ultimately contingent upon the operation of hydrodynamic and sedimentary processes within constraints imposed by the available accommodation space and sediment supply this paper re interprets published data relating to contemporary vertical marsh growth and sea level rise in the context of the conceptual model relating elevation sedimentation sea level rise sediment supply and tidal range this analysis is supported by numerical mass balance modelling of the equivalent parameter space and of the sensitivity of marsh hydroperiod and sedimentation to sea level and sediment supply forcing the effect of autocompaction on the translation of sedimentation into elevation change is also considered parameter space modelling provides a framework for the interpretation of field data and affords indicative insights into marsh resilience to change it is argued that the assessment of marsh response to external environmental forcing should be based not on empirical comparisons of sedimentation versus sea level rise but on the estimation of sediment supply and the efficiency with which this is depleted by deposition as metrics of marsh resilience this implies a shift towards more intensive process studies aimed at elucidating more fully the linkages between tidal marshes and adjacent estuarine and coastal systems model results also indicate significant variability in marsh sedimentation associated with 18 6 yr tidal modulation and meteorological processes at short term scales such variability further complicates the interpretation of sedimentation or elevation change data obtained from monitoring programmes of short duration longer term monitoring is of value however as a means of identifying important mechanisms of climate and sediment supply forcing that may contribute to the formation and maintenance of marsh sedimentary sequences

a 17 yr record of sediment accretion in the salt marshes of maine usa abstract marker horizons of brick dust were established in 1986 in 26 salt marshes along the coast of maine usa in 2003 we measured the sediment accumulation rates for the 17 year period in 11 relocated sites and obtained results varying from 1 4 to 4 2 mm yr the mean accretion rate for all marshes was 2 8 mm yr accretion rates measured from 1986 to 2003 were comparable to those measured at the sites in 1987 and 1990 indicating that marsh accretion rates are similar on annual and decadal time scales inorganic material was found to be the primary constituent of maine salt marsh sediments several marshes show clear evidence of transgression since 1986 in the form of landward moving plant zones or encroachment of mudflat onto salt marsh indications for regressive changes were not observed marsh sediment accumulation rates are generally higher than mean rates of relative sea level rise indicating that most salt marshes are currently keeping pace with sea level rise however if relative sea level rise were to exceed rates of 4 mm yr many salt marshes in maine may not survive

on interseismic elevation changes and strain accumulation for great thrust earthquakes in the nepal himalaya estimates of interseismic ground elevation change rates from nepal himalaya based on repeat levelling observations between 1977 and 1990 in the meizoseismal zone of the great thrust earthquake of 1934 have been reported by jackson and bilham 1994 we explain them using the model of savage 1983 for seismic strain accumulation and release along plate boundary faults pbf at convergent plate margins thus the section of the pbf under the nepal himalaya that ruptured during the 1934 earthquake may be currently locked and the hanging wall rocks may be experiencing downdip drag at the local plate convergence rate three independent estimates of 150 100 and 50 km for downdip rupture width during the 1934 earthquake are available if we use them as estimates of the current width of the locked zone in nepal then values of 18 14 and 12 mm year respectively for the plate convergence rate are obtained although all these values compare favourably with the estimated long term average rate of 18 7 mm year for plate convergence accommodated at the himalaya the rms error is the least for the model with 150 km width of the locked zone

towards an integrated land sea stratigraphy of the netherlands abstract the classification of rocks and sediments may be based on many types of stratigraphy e g litho bio seismo chrono chemostratigraphy and others the boundaries of the various types of stratigraphy need not at all or seldom coincide it is especially this last consideration that may cause problems since this discrepancy in boundaries is very difficult to understand for those not professionally trained as geologists since tno nitg as the dutch geological survey is an organisation for applied geosciences it is necessary that full notice is taken of this problem a complete revision of the existing late tertiary and quaternary lithostratigraphy of the onshore part of the netherlands which was a mixture of various types of stratigraphies was undertaken starting in 1997 at the same time the opportunity was taken to integrate this new scheme with the two other operational stratigraphies used by tno nitg important solutions in resolving some of the integration problems are outlined an example of the relation between some of the newly established lithostratigraphic units with some of the seismostratigraphic ones used in the offshore part of the netherlands is given finally an example of the implications of the new approach for the existing geological model is presented

seismotectonics of the great 1905 kangra earthquake meizoseismal region in kangra chamba nw himalaya abstract three great earthquakes with magnitude greater than 8 have struck the himalayan belt within a span of 50 years and the 1905 kangra earthquake is one of them the seismotectonics of the meizoseismal region of this earthquake in the kangra chamba region are analyzed on the basis of the major structures and the present day seismic activity the microseismicity recorded by a network of 12 stations for a period of 16 months spanning 4 years 1993 1996 shows the activity is mainly concentrated over the main boundary thrust mbt and panjal thrust pt zones and the chamba nappe region a ne sw vertical section reveals that the majority of events are concentrated within a depth range of 5 to 18 km and the majority of the foci lie between 12 and 18 km the base of the microseismicity zone is interpreted as representing a contact or a decollement plane between the top of the indian plate and the himalayan rock formations this decollement plane is interpreted as the northern continuation of the detachment observed in the sub himalaya in reflection profile the southward propagation of the chamba nappe as well as the pt and mbt zones over the detachment causes accumulation of strain energy in this region

relationships among vertical accretion coastal submergence and erosion in a louisiana gulf coast marsh abstract vertical accretion in a southwest louisiana spartina patens brackish marsh has not kept pace with coastal submergence during the past three decades the rate of accretion determined from 137cs dating and the use of artificial marker horizons averaged 0 8 cm yr 1 whereas coastal submergence obtained from tide gauge data averaged 1 2 cm yr 1 conversion from marsh to open water bodies closely paralleled the increase in coastal submergence if the resulting aggradation deficit continues the marsh will likely complete its transformation to an open bay in less than 40 years in view of recent projections of increasing sea level rise the results presented may foreshadow a more widespread phenomenon

avulsions channel evolution and floodplain sedimentation rates of the anastomosing upper columbia river british columbia canada ages of channels of the anastomosing upper columbia river south eastern british columbia canada were investigated in a cross valley transect by c 14 dating of subsurface floodplain organic material from beneath levees the avulsion history within the transect was deduced from these data and morphological stages in channel development were recognized additionally floodplain sedimentation rates were established the new data demonstrate that the upper columbia river is a long lived dynamic anastomosing system results show that anastomosis at the study location has persisted since at least 2700 cal years bp with avulsions occurring frequently at least nine channels have formed in the studied cross valley transect within the past 3000 years channel lifetimes from formation to abandonment appear to be highly variable ranging from approximately 800 to 3000 years log jams provoking avulsions and or silting up of old channels are proposed as reasons for this variability long term average floodplain sedimentation rates appear to be significantly lower than previously proposed by smith 1983 int assoc sedimentol spec publ 6 155 168 a long term 4550 years average of 1 75 mm per year after compaction was based on c 14 dates whilea short term sedimentation rate of 0 8 mm was determined for a single relatively small seasonal flood in 1994 using sediment traps however short term sedimentation rates vary considerably over the floodplain with levees aggrading up to four times faster than floodbasins channels of the upper columbia river anastomosed reach follow a consistent pattern in their development with each stage being characterized by different morphology and processes channel evolution comprises the following succession 1 avulsion stage in which a crevasse splay channel deepens by scour and levee sedimentation 2 widening and deepening stage in which bank slumping and bed scouring dominates 3 infilling stage in which either channel narrowing bank accretion or channel shallowing bed accretion takes place and 4 abandonment stage in which the residual remnant channel is filled exclusively by silt clay and organic material vertical stacking super imposition of active channels on recent channel fill sand bodies is a notable feature of the upper columbia river which suggests that reoccupation of residual channels is a common process

paleoseismic investigation along nalagarh thrust evidence of late pleistocene earthquake in pinjaur dun northwestern sub himalaya abstract the present article is the first time reporting of a paleoearthquake that occurred during late pleistocene time along the nalagarh thrust nt in the pinjaur dun in northwestern sub himalaya using corona satellite photographs multi spectral irs satellite data and aerial photographs a prominent active fault has been identified at nalagarh in pinjaur dun this fault in the alluvial fan is located very close to the nt which borders the topographic front of the tertiary rocks against quaternary deposits a trench excavation survey was carried out at nalagarh for detailed paleoseismic studies across this thrust fault displacing all the lithologic units of the fan sequence the fault plane has an average dip of 30 due ene and a vertical displacement of 1 6 m and slip of 2 5 m along the fault the lithological units consisting of alternating sand and gravel show back tilting and asymmetrical tight folding based on optically stimulated luminescence osl ages the oldest litho unit in the trench is 85 83 7 2 ka and the youngest is 67 05 8 4 ka the osl age of the sample collected from the easterly exposure of the fault shows an age of 20 ka the faulting and associated induced deformation features suggest occurrence of a late pleistocene large magnitude earthquake along nt in the nalagarh region of the pinjaur dun following the deposition of the quaternary sedimentary units the late pleistocene fault substantiates the seismic potential of pinjaur dun and calls for more exhaustive study of paleoearthquakes in this fast developing industrial belt and highly populous mountainous region

seismicity and the state of stress from investigations of local earthquakes in the kumaon himalaya abstract results of investigations of local earthquakes in the region of the main central thrust mct in the kumaon himalaya between and adjacent to the valleys of the bhagirathi and yamuna rivers are presented records of over 250 earthquakes were analysed and the following facts emerged 1 1 earthquakes in the himalayas occur in specific areas and belts one such belt has been identified in the region under investigation hypocentral estimates being more reliable for earthquakes occurring in the middle segment approximately 70 km long of this belt crossing the yamuna river between the villages of barkot and syanachatti 2 2 all but a few epicentres in this middle segment lie to the southwest of the surface trace of the mct in a zone with a width of 10 30 km 3 3 most of the earthquakes in this segment occur at depths of less than 10 km below the ground surface the maximum estimated depth being 32 km using observations of first motion for a composite focal mechanism solution the nodal planes were observed to be near vertical and the compression axis near horizontal and normal to the local strike of the seismic belt and of the mct we conclude that although the main central thrust itself is not seismically active in this region there is considerable activity immediately to the southwest of it furthermore the mode of faulting as inferred from the records of these earthquakes is strike slip