esr dating of the neanderthal site kebara cave israel abstract in 1985 a neanderthal skeleton was found in the cave of kebara in southern mt carmel electron spin resonance esr dates have been obtained on tooth enamel of gazelles found in layer x just overlying the layer in which the skeleton was found assuming early uptake of uranium by the teeth they yield an age of 60 6 ka assuming gradual linear uptake of uranium yields an age of 64 6 ka both age estimates are consistent with a previous estimate for the skeleton based on tl dating of burnt flint of 60 4 ka

shallow sub surface stratigraphy of the ganga basin himalayan foreland present status and future perspectives the ganga basin in northern india is one of the world s largest fluvial basins and has attracted enormous attention from earth scientists across the globe with a view to understanding large river processes and landforms despite the scarcity of hydrological data from the ganga basin some important studies have been carried out in the last several decades however the unavailability of deep sections in this vast alluvial tract has always limited understanding of the sub surface stratigraphy of these plains during the last decade some important developments have taken place in integrating exposed cliff section data with the drill cores in pre defined transects and with targeted geophysical investigations additionally new areas of the basin have been studied for understanding landscape evolution including the effects of active tectonics this special issue of quaternary international highlights some of these developments from the stratigraphic archives of this large basin this collection of papers covers a wide gamut of subjects including terrace development in the frontal parts of the ganga basin resistivity based mapping of sub surface stratigraphy micromorphology of soils from plains drill core samples historical scale avulsion of large dynamic system such as the kosi active tectonics and landform development in southern ganga plains and finally some policy issues for management of dynamic river systems this introductory paper provides a background and present status of research in the ganga basin it attempts to summarise some of the recent research developments in the ganga basin research and highlights the unresolved issues some of which have been addressed through the contributions in this special issue

external dose rate determinations for esr dating at bau de l aubesier provence france abstract at bau de l aubesier provence france mousterian artefacts and human teeth occur in inhomogeneous lumpy sedimentary deposits that include bone and tooth fragments due to uranium u uptake by the bones and teeth the external dose rate experienced by the teeth has changed over time such changes must be considered when calculating thermoluminescence tl ages for burnt flint artefacts or electron spin resonance esr ages for the teeth therein here we assess the external dose rates using three methods in situ tl dosimetry gives the modern dose rate whereas volumetrically averaged geochemical analysis is used to estimate time averaged dose rates that consider u uptake by u rich sedimentary components blackwell and blickstein 2000 quarternary international 68 71 329 343 in esr isochron analysis blackwell and schwarcz 1993 applied radiation and isotopes 44 243 252 multiple subsamples with variable u concentrations measure the external dose rate experienced by the tooth regardless of reworking but do depend on the uptake model assumed the methods each suggest significantly different dose rates tl dosimetry for two combustion horizons measured external dose rates at 0 143 0 012 mgray y in layer iv and 0 184 0 016 mgray y in layer h geochemical analysis when volumetrically averaged to account for the influence from different sedimentary components indicates external dose rates ranging from as low as 0 094 0 024 mgray y assuming ru for u rich sedimentary components to a maximum of 0 251 0 048 mgray y assuming eu for the u rich components isochron analyses suggest more variable dose rates ranging from a minimum of 0 009 0 040 mgray y lu in the lower layers to a high of 1 103 0 160 mgray y eu in layer h1 three isochrons indicated that the teeth had experienced u leaching or a second uptake event which would affect the accuracy of the dose rate determinations for those teeth other teeth may have experienced similar processes quaternary researchers who want reliable dates in the age ranges for esr or tl must carefully consider both the nature of the sediment especially u rich bone fragments and its geometric arrangement around the samples to be dated corresponding results using more than one analytic method may be required for a reasonable confidence level

the stone source of predynastic basalt vessels mineralogical evidence for quarries in northern egypt abstract about 22 of all predynastic stone vessels are basaltic in composition as a result of their nondescript petrography the raw material source of these common artefacts is challenging to determine electron microprobe analyses of pyroxene and plagioclase in 0 0001 g samples from nine predynastic basalt vessels indicate compositions consistent with an origin from haddadin basalt outcrops west of cairo the raw material or finished vessels were transported 600 km up the nile to abydos and qena bypassing closer basalt sources in middle egypt these results and stylistic considerations indicate that a major vessel manufacturing industry existed in northern egypt but the location of the workshops has yet to be found quarrying of haddadin basalt for vessels spanned at least 900 years accessibility and breakage characteristics of the basalt help account for its prolonged and widespread use but basalts in middle egypt may have similar properties suggesting that either tradition or some unidentified physical quality was also important this study underscores the utility of the electron microprobe for fingerprinting basalt flows the factor equations and discrimination diagrams allow the stone source for egyptian basaltic artefacts to be determined on a more routine basis it is not necessary to re sample the quarries and obtain hundreds of mineral analyses to determine a source miniscule amounts of material are required making the method applicable even to extremely valuable antiquities

late quaternary sedimentary environments and landforms in the ganges delta abstract late quaternary sediments deposited since the lowest stand of sea level during the last glacial maximum in the ganges delta and its surrounding region were classified into five units according to their sedimentary facies these are the lowest unit of sandy gravels the lower unit of sand with a few gravels and the middle upper and uppermost units consisting mainly of sand and silt with occasional peat layers the contact between the lower and middle units is fairly sharp and the upper part of the lower unit is oxidized in some places this suggests a period of subaerial exposure after the deposition of the lower unit during the low stand of sea level about the time of the last glacial maximum rivers in the ganges delta and its surrounding region dissected the surfaces of the region and deposited the lowest unit on the valley floors the lower unit was deposited over the lowest unit during an early stage of the post glacial transgression between ca 12 000 yr bp and 10 000 yr bp the surface of the delta was slightly dissected and the top of the lower unit was weathered and oxidized following this period the middle and upper units of alluvial or deltaic sand and silt with occasional peat were deposited the coastline in the early holocene retreated towards the central part of the present ganges delta in the middle and late holocene the silt and clay with occasional peat layers of the uppermost unit indicate that the lowland gradually became marshy and poorly drained as the rate of transgression became slower

chert from the munsungun lake formation maine in palaeoamerican archaeological sites in northeastern north america recognition of its occurrence and distribution abstract numerous fluted point palaeoamerican sites in the northeast contain significant numbers of chert artefacts whose origin is from the munsungun lake formation in northern maine these sites include adkins bull brook dam hedden lamareau michaud morss munsungun lake three sites neponset plenge point sebago searsmont spiller farm vail vail kill two sites wheeler dam two sites and whipple lithic materials in order of decreasing importance at these sites include 1 chert whose physical characteristics are wholly consistent with chert outcrops and quarries near munsungun lake 2 a variety of cherts whose physical characteristics are inconsistent with outcrops and quarries near munsungun lake 3 a spherulitic flow banded rhyolite 4 miscellaneous fine grained igneous rocks 5 clear or milky quartz 6 miscellaneous very fine grained or fine grained metamorphic rocks portions of all collections contain artefacts which are completely weathered and which are not assignable to any specific rock type and cannot be classified as to specific rock type we developed a hierarchy to classify munsungun lake chert ranging from hand specimen characteristics to polarized light microscopy and x ray diffraction to chemical analysis we conclude that hand specimen characteristics combined with polarized light microscopy are viable techniques for assigning munsungun lake formation provenance three distinctive hand specimen features are sedimentary lamination organic burrow structures and colour variation using these chert quarries and outcrops in the geographic vicinity of munsungun lake may be assigned to one of the following categories a structureless grayish red dusky red blackish red or dark reddish brown b laminated grayish red dusky red blackish red or dark reddish brown chert with varve like laminations c mottled or colour laminated red and dark grey or mottled red and greenish grey chert d colour laminated and burrow mottled chert e greyish to blackish laminated chert f dark grey to black structureless or weakly and thinly laminated g olive grey to olive black laminated chert which is locally pyrite rich the nature of weathered surfaces may be a diagnostic tool for assistance in recognizing munsungun chert chemical weathering tends to produce much lighter colourations and enhances the visibility of sedimentary structures munsungun cherts tend to weather to a very light tan very light grey or greyish white radiolarians are uncommon chert palaeoquarries are numerous in the munsungun lake area they are of two types one type occurs on topographically flat areas here the quarries are small 1 5 m to large 5 30 m size depressions within and along outcrops in plan view these range in shape from roughly circular to broad ovals along the margins of these depressions are piles of poorly sorted worked and discarded debitage these tailing piles are generally less than 1 m in height but exhibit wide variations in areal extent and shape larger tailing piles overlap one another suggesting that they have experienced more than one episode of growth due to repeated quarry activity the second quarry type occurs on steeper slopes these are near vertical quarried faces which range from 1 to nearly 3 m in height excavation here has occurred both inwards to the slope and downwards small cavern or adit like mines have not been recognized

comment on neutron activation analysis of stone from thechadron formation and a clovis site on the great plains by hoard et al 1992 abstract comments are made on the previously published paper by hoard et al neutron activation analysis of stone from thechadron formation and a clovis site on the great plains journal of archaeological science 19 655 665 1992 a number of questions and their implications are discussed

chemical characterization of obsidians from different mediterranean sources by non destructive sem eds analytical method the aim of our research is to check the sem eds non destructive analytical method for discriminating and locating the possible sources of obsidian artefacts moreover in order to obtain a significant discrimination of mediterranean obsidians we analysed samples collected from outcrops of the major sources monte arci sardinia and palmarola lipari pantelleria gyali and melos islands all samples were analysed by both xrf whole rock and sem eds glass and microliths microphenocrysts the xrf analysis reveals that major elements discriminate obsidian the discrimination using major elements is very useful because the amount of trace elements is lower than the detection limit of a si li ed detector the major elements particularly sio2 al2o3 cao na2o and k2o of obsidian glass discriminate the six main mediterranean sources our work demonstrates therefore the possibility of discriminating different provenance of obsidian artefacts using sem eds by means of a relatively rapid effective and above all non destructive method

signatures from single airguns the far field signatures from a comprehensive and systematic airgun pulse test have been analyzed empirical relations between the characteristic signature parameters and depth 5 12 m pressure 100 137 bar 10 13 7 mpa and total chamber volume 0 65 9 5 l have been derived also the influence of using waveshape kits in different positions within the chamber has been tested the results indicate that 1 the amplitude is proportional to chamber pressure to the power 3 4 2 the bubble period is nearly independent of the position of the waveshape plate 3 the increase in primary bubble amplitude ratio is inversely proportional to the chamber volume above the waveshape plate 4 the amplitude is independent of airgun depth suggestions and comments regarding this work from dr b ursin and dr a ziolkowski are appreciated the field work was supported by the norwegian petroleum directorate through the continental shelf project at the seismological observatory university of bergen an airgun allowing for continuous variation of the chamber volumes was supplied by geco geophysical company of norway the purchase of two airguns was financed by norske getty exploration a s

river channel change during the last 50 years in the middle yangtze river the jianli reach intensive anthropogenic disturbances have affected the channel of the middle yangtze river since the 1950s this paper selects the jianli reach as an example to examine human impact on channel change in the middle yangtze river 1 100 000 channel distribution maps from 1951 1961 and 1975 and 1 25 000 navigation charts from 1981 and 1997 were employed to reconstruct channel change in the study reach the result indicates that the channel under the constraint of levees along the riverbanks underwent a minor widening but frequent bank failure due to susceptible bank structure and increase in water discharge the bank failure promoted bar growth in the channel cross section changes and quantitative calculations of erosion and deposition based on the dem derived from navigation charts present a pattern of over bank sedimentation and riverbed incision the stage and duration of floods have increased following levee construction and bank revetment

obsidian characterization by laser ablation icp ms and its application to prehistoric trade in the mediterranean and the near east sources and distribution of obsidian within the aegean and anatolia for geological studies interest in mass spectrometry with an inductively coupled plasma as an ion source and its association with laser ablation as a sample introduction technique la icp ms has steadily increased during the past few years and is now being developed in other fields such as archaeology after a description of the analytical procedure and the calculation method we show the potential of this technique to characterize almost non destructively archaeological artefacts among the 70 elements that could be routinely analysed by la icp ms with detection limits below the ppm level we choose to determine the more critical ones in order to evaluate the geochemical models of the magmatic process major elements rare earths and some transition elements a detailed survey of cappadocian obsidian flows is given and includes the characterization of nine different sources evidence of complex trade activities is clearly shown by the obsidian tools found at different prehistoric sites from neolithic to bronze age levels in the mediterranean and the near east new results obtained on some archaeological sites located in turkey syria and cyprus are presented they show the importance of cappadocian sources in obsidian trade our results show that la icp ms allows a non destructive analysis of archaeological objects and that it combines the advantage of the different classical methods used to characterize obsidian sources mainly xrf and inaa with high sensitivity and rapidity thus la icp ms appears to be a very powerful analytical tool and at this time this technique is the only one which can non destructively determine such an important number of elements with such low detection limits

assessing channel changes of the ganges padma river system in bangladesh using landsat and hydrological data abstract the ganga ganges 1 is an important river system in south asia which supports the life and livelihoods of millions of people both in india and bangladesh the system has a number of names throughout its length below its confluence with the brahmaputra at aricha it is known as the padma which in turn merges with the upper meghna at chandpur below which the channel is known as the lower meghna there is a growing concern about this large river system because its channels are subject to frequent migration threatening engineering structures and resulting in various environmental and social consequences which may be compounded by climatic variability land use change and agricultural intensification as the basin experiences rapid population growth concerns have been expressed that the construction of a barrage just upstream of the indo bangladesh border has adversely affected the ganges reach in bangladesh partly in order to investigate this the planform changes of the ganges and the padma within bangladesh was analysed over the period 1973 to 2011 using multitemporal landsat images and long term flow data in eight epochs with an average duration of 4 5 years the padma reach is less affected by the barrage and provides a useful control study areas of erosion and deposition were determined from sequential changes in the bankline positions mean channel width sinuosity and braiding index were analysed using a geographic information system gis flood frequency duration and magnitudes were studied using long term discharge records generally channel planform evaluation indicated that both the ganges and the padma experienced contraction expansion and readjustment in configuration over the last 38 years erosion and deposition statistics of the ganges indicate that 57 km2 of land was lost along the right bank whereas around 59 km2 has been gained along the left bank during the assessment period suggesting that the erosion and accretion of both banks is roughly balanced with a general movement towards the right bank the width of the ganges varied from a maximum of 5 36 to a minimum of 3 23 km during the observation period changes to sandbar area are in general much more radical than changes to the overall width and area of the channel measurement of areas of erosion and accretion showed that both banks of the padma experienced considerable loss of land the total net loss for left bank and right bank was 155 and 28 km2 respectively the padma is approximately twice the width of the ganges and the changes to its channel area are not as temporally dynamic as the ganges the relationship between bank curvature and erosion accretion of the river banks for both rivers was analysed and the results contradict established meander theory regression analysis between bank erosion rates annual average discharge and mean flood flow data showed that bank erosion was significantly correlated with annual average discharge for the padma r2 0 6283 and that the ganges bank erosion rate is influenced by mean flood flow r2 0 6738 the flood frequency shows generally good stability across the first eight of the nine epochs for the ganges but for the padma the frequency showed even greater stability we were unable to support the widely held belief that the upstream barrage has a deleterious effect on the ganges but note that there is a slight effect due to the periodic release of sediment through scour sluices

a combined visual geochemical approach to establishing provenance for pegmatite quartz artifacts a technique for establishing source provenance for pegmatite quartz artifacts was developed using a quarry sample from the churchill river basin of northern manitoba and saskatchewan secondary ion mass spectrometry sims was used to quantify ti ge th and u trace element concentrations and pb isotope ratios coupled with qualitative visual characteristics to distinguish between pegmatite quartz from different archaeologically exploited sources in the churchill river basin region the technique was also applied to a small sample of quartz artifacts recovered from sites in and around the study area in a preliminary attempt to assign or rule out raw material provenance to characterized sources

inaa of pre contact basalt quarries on the samoan island of tutuila a preliminary baseline for an artifact centered provenance study abstract this project presents a material centered instrumental neutron activation analysis inaa characterization of 120 geologic samples selected from four fine grained basalt quarries on the samoan island of tutuila previous attempts at definitive differentiation of these tutuilan quarries have utilized x ray fluorescence xrf in this study clear differentiation of each analyzed quarry was achieved using inaa biplots of canonical discriminant analysis cda scores for the inaa data illustrate clear separation based on the variation in chemical composition between each quarry the samples analyzed not only define quarry separation but also provide the core group for a preliminary baseline necessary for future artifact centered provenance studies inclusion of these core group samples in the baseline was confirmed by stepwise discriminant analysis these findings suggest the ability to determine artifact quarry of origin on the island of tutuila which can elucidate the importance of individual tutuilan quarries in the production distribution and consumption of fine grained basalt artifacts in polynesia

glaze and slip pigment analyses of pueblo iv period ceramics from east central arizona using time of flight laser ablation inductively coupled plasma mass spectrometry tof la icp ms this paper presents the results of glaze paint and slip analysis of 161 white mountain red ware ceramic samples ad 1275e1325 from east central arizona time of flight laser ablation inductively coupled plasma mass spectrometry tof la icp ms analysis is used 1 to establish viability of the technique for measuring chemical compositions of glazes and slips and 2 to establish a methodology for inferring this structured variability specifically delineating the presence of specific pigment mixtures or recipes used by prehistoric potters in the greater southwest these data bear on archaeological questions about craft production exchange technology and social organization 2006 elsevier ltd all rights reserved

la icp ms analysis of clovis period projectile points from the gault site abstract a key tenet of clovis period hunter gatherer mobility is the utilization of large ranges based on the appearance of exotic raw materials particularly chert in clovis assemblages the identification of the sources of chert in clovis period assemblages is problematic as it has relied on macroscopic properties macroscopic characteristics of chert can be highly variable in a single outcrop occur across very large areas and have correlates in unrelated and far removed contexts an instrumental geochemical approach was utilized that potentially offers advances in the capacity to link chert artifacts to their sources trace element data was recovered from 33 clovis period projectile points from the gault site 41bl323 using laser ablation inductively coupled plasma mass spectrometry la icp ms this data was compared to trace element data recovered from 224 primary geologic samples of chert from multiple primary sources across the edwards plateau in texas the clovis points were compared to the geologic sources using canonical discriminant analysis to establish group membership at three spatial scales macro regional greater than 500 km regional between 30 and 500 km and local between 1 and 30 km it was found at the macro regional scale that 21 of the 33 clovis points were to be geochemically similar to edwards plateau sources at the regional scale 15 of the 21 identified edwards plateau clovis points could be attributed to a particular source lastly only two clovis points could be identified to particular sources at the local scale

implementation of marine seismic source wavefields in finite difference methods using wavefield injection abstractwe have developed a method for implementing source wavefields in finite difference fd schemes for marine seismic modeling migration and inversion by using the wavefield injection technique it is possible to inject arbitrary source wavefields into an fd grid we have assumed that the notional source signatures from each gun in an air gun array and their positions are known the source wavefield is extrapolated to a specified surface below the true source positions using analytical green s functions on this surface the pressure and its vertical derivative are inserted into the fd grid the wavefield propagating from this surface will then propagate downward and appear as if it came from the true source position the source positions do not need to coincide with the fd grid points and the free surface reflection coefficient for the source ghost can be specified i e it can deviate from 1 and it can be frequency dependent these features are possible because of the analytical extrapolatio

chipped stone artefacts source areas and provenance studies of the northern belize chert bearing zone previous studies of the northern belize chert bearing zone which was widely exploited by the ancient maya for the production of chipped stone artefacts have suggested that chert from different parts of this zone might be chemically distinct this hypothesis is tested with an expanded data base of neutron activation analyses of raw chert and chalcedony from throughout northern belize these data together with data from previous studies indicate that the chert bearing zone is one chemically homogenous source and that meaningful distinctions cannot be made between different areas of the zone a more specific lithic source hypothesis is that the black chipped chert and chalcedony artefacts found at coastal maya sites in northern belize may come from a localized source area exhibiting this unique visual characteristic however the analysis conclusively demonstrates that these artefacts fall within the range of chemical variation of other chert and chalcedony from northern belize further the study yields convincing evidence that the colouration of these black lithic artefacts is caused by a weathering phenomenon and hence is not indicative of a particular source location

medium and short term channel planform changes on the rivers tay and tummel scotland abstract channel planform change was analysed using a variety of data sources for the medium term 25 years and

evolutionary multi scale analysis of river bank line retreat using continuous wavelet transforms jamuna river bangladesh in this study continuous wavelet transforms are used to explore spatio temporal patterns of multi scale bank line retreat along a 204 km reach of the jamuna river bangladesh a sequence of eight bank line retreat series derived from remotely sensed imagery for the period 1987 1999 is transformed using the morlet mother wavelet bank erosion is shown to operate at several characteristic spatial and temporal scales local erosion and bank line retreat are shown to occur in short well defined reaches characterised by temporal persistence at the same location and separated by relatively stable reaches in contrast evidence of downstream propagation of bank line retreat patterns is evident at larger spatial scales the intensity of localised bank line retreat i e at scales of 0 20 km is strongly related to the magnitude of monsoonal peak discharge but this relationship weakens as the spatial scale of erosion increases the potential of continuous wavelet analysis to enhancing our understanding of morphological evolution in complex fluvial systems with multi channel planforms is discussed

three dimensional sedimentary architecture of a large mid channel sand braid bar jamuna river bangladesh the three dimensional subsurface alluvial architecture of a large approximately 3 km long 1 km wide 12 m high mid channel sand braid bar in the jamuna river bangladesh is described evolution of the bar and its depositional characteristics are assessed from a unique combination of ground penetrating radar surveys vibracoring and trenching that are allied to a series of bathymetric surveys taken during growth of the bar over a 29 month period this methodology permits identification of the formative processes of different packages of braid bar sedimentation and provides a facies model for deposition within the entire bar mid channel bar growth occurred in a region of flow expansion and was probably initiated by the stalling and amalgamation of large dunes these dunes created a bar core that grew by i propagation of a downstream accreting slipface ii vertical accretion through stacking of dunes on both bar stoss and top and iii lateral accretion on the bar margins during recession of the flood hydrograph braid bar sedimentation is dominated by four radar facies 1 large scale predominantly planar dipping reflections interpreted as cross stratification up to 8 m in height and greater than 100 m in width that is produced by the cross channel migration of bar margins 2 medium scale trough shaped and planar discontinuous reflections interpreted as cross stratification up to 4 m in height and 300 m wide that is deposited from large sinuous crested sand dunes 3 discontinuous reflections up to 2 m high and 30 m wide interpreted as small scale trough cross stratification that is the product of smaller sinuous crested dunes and 4 high amplitude undulating reflections interpreted as mud drapes deposited in regions of slow flow often in the bar tail region at low stage dune size decreases vertically within the bar in response to the progressively shallower flows on the emerging bar top later evolution of the bar as one anabranch channel became dominant created a 1 5 km extension to the bar tail with an 8 m high angle of repose bar margin slipface formed by flow transverse to the long axis of the bar seven styles of deposition can be defined that constitute the alluvial architecture bar margin slipface vertical accretion in channel bar top vertical accretion upstream accretion lateral accretion downstream accretion and low stage mud drapes a model of braid bar sedimentation is presented that shares many similarities with previous studies of smaller sand bed braid bars with the dominance of dune scale cross stratification the presence of large scale bar margin cross stratification and the occurrence of lateral vertical upstream and downstream accretion however the contribution of the bar margin facies to the preserved stratigraphy highlighted herein may have been underestimated in previous models of braided rivers in which the braid bars were migrating slowly this study suggests a scale invariance in several aspects of mid channel bar sedimentation in sand bed rivers and proposes a model of braid bar sedimentation that may be applied widely within studies of braided alluvial architecture

morphological evolution and dynamics of a large sand braid bar jamuna river bangladesh the initiation and evolution of a kilometre scale sand braid bar was monitored during a 28 month survey period from 1993 to 1996 in one of the world s largest braided rivers the jamuna river bangladesh repeated bathymetric surveys through two monsoon flood seasons combined with bar top surveys during exposure of the bar at low flow provide the most detailed chronology of braid bar growth yet compiled for a large sand bed river during rising and peak flow of the 1994 monsoon flood a 1 5 km long 0 5 km wide 12 m high symmetrical mid channel bar was deposited in the centre of a major channel downstream of a zone of flow convergence and significant bank erosion initial deposition and growth of the bar core were probably caused by amalgamation of dunes that are present in the jamuna channels at all flow stages bar top aggradation continued through downstream migration of an accretionary dune front a 3 m high angle of repose slipface that was composed of amalgamated 0 5 to 1 m high dunes at waning and low flow the mid channel bar widened by up to 1 km through the lateral accretion of dunes onto the margins of the initial bar core a low velocity zone in the sheltered wake region of the bar tail led to the accumulation of substantial volumes of silts and clays during the rising and peak flows of the next monsoon flood the mid channel bar extended its bar tail by up to 1 5 km as one of the anabranches became dominant and flow was deflected across the bar tail accretion at the bar tail generated a lobate transverse bar front with a 10 m high angle of repose avalanche face emergence of several smaller bars along this depositional front produced an overall reach morphology that more closely resembled an alternate bar rather than several mid channel bars the conversion of a mid channel bar to an alternate bar is contrary to many previous descriptions of the braiding process

neutron activation analysis of stone from the chadron formation and a clovis site on the great plains abstract cryptocrystalline silicates from the chadron formation were widely used by prehistoric human groups in the great plains of north america there are two documented quarry areas flattop butte in colorado and the white river badlands of south dakota cryptocrystalline silicates from these sources are visually indistinguishable making it difficult to determine the sources of artefacts found at archaeological sites in this investigation neutron activation analysis is used to distinguish the two sources this technique also identifies lithic material from the clovis age eckles site in kansas as being from flattop butte

channel and island change in the lower platte river eastern nebraska usa 1855 2005 abstract the lower platte river has undergone considerable change in channel and bar characteristics since the mid 1850s in four 20 25 km long study stretches the same net effect of historical channel shrinkage that was detected upstream from grand island nebraska can also be detected in the lower river but differences in the behaviors of study stretches upstream and downstream from major tributaries are striking the least relative decrease occurred downstream from the loup river confluence and the stretch downstream from the elkhorn river confluence actually showed an increase in channel area during the 1940s bank erosion was also greater downstream of the tributaries between ca 1860 and 1938 1941 particularly in stretch rg which showed more lateral migration the cumulative island area and the ratio of island area to channel area relative to the 1938 1941 baseline data showed comparatively great fluctuations in median island size in both downstream stretches the erratic behavior of island size distributions over time indicates that large islands were accreted to the banks at different times and that some small newly stabilized islands were episodically flushed out of the system in the upstream stretches the stabilization of mobile bars to create new small islands had a more consistent impact over time channel decrease by the abandonment of large long lived anabranches and by the in place narrowing resulting from island accretion were more prominent in these upstream stretches across all of the study area channel area appears to be stabilizing gradually as the rate of decrease lessens this trend began earliest in stretch rg in the late 1950s and was accompanied by shifts in the size distributions of stabilized islands in that stretch into the 1960s elsewhere even in the easternmost study stretch stabilizing was occurring by the late 1960s the same time frame documented by investigations of the platte system upstream of the study area comprehensive management plans for the lower platte river should account at least in theory for the observed differences in stream behavior upstream and downstream of the major eastern tributaries

broadband seismic over under sources and their designature deghosting abstractthe source depth influences the frequency band of seismic data due to the source ghost effect it is advantageous to deploy sources deep to enhance the low frequency content of seismic data but for a given source volume the bubble period decreases with the source depth thereby degrading the low frequency content at the same time deep sources reduce the seismic bandwidth deploying sources at shallower depths has the opposite effects a shallow source provides improved high frequency content at the cost of degraded low frequency content due to the ghosting effect whereas the bubble period increases with a lesser source depth thereby slightly improving the low frequency content a solution to the challenge of extending the bandwidth on the low and high frequency side is to deploy over under sources in which sources are towed at two depths we have developed a mathematical ghost model for over under point sources fired in sequential and simultaneous modes and we have found an inverse mode

in the footsteps of pliny tracing the sources of garamantian carnelian from fazzan south west libya abstract references in the ancient sources indicate that the libyan desert was a source of carbunculi semi precious red stones and gemstones variously interpreted as ruby garnet and spinel amongst others while gemstones are not attested in the geological strata of fazzan south west libya a range of silica based stones including chert chalcedony agate and carnelian are known to originate in this area linked to an early civilisation known as the garamantes it has been long proposed that the geochemical signature and the variations in the relative proportions of quartz moganite phases can be used to distinguish between groups of stones of different origin the proposed methodology was tested on a number of archaeological samples from the garamantian sites of jarma ancient garama and saniat jibril in fazzan fragments of chert carnelian and amazonite found at the two sites have been identified as raw materials associated with beadmaking trace elemental data obtained by la icp ms were combined with mineralogical data obtained by x ray powder diffraction and raman spectroscopy on the same samples and a group of reference samples the dataset has been compared with the available literature and data from other localities around the world to this purpose a preliminary database of silica based materials was established for provenance work based on the scarce data available in the literature the importation of these stones from eastern localities such as india may be ruled out the measured data on archaeological samples and debitage allow us to define a reliable reference group of parameters for materials from fazzan which are likely to be derived from a unique geological source the methodology should be extended and compared with cherts and carnelians from a range of mediterranean and sub saharan sites this characterisation work is a tool of high potential utility for a new investigation of ancient contact and trade across the trans saharan zone

tl dates for the neanderthal site of the amud cave israel abstract age estimates ranging from 50 to 70 ky were obtained for the mousterian deposits of amud cave in israel from thermoluminescence measurements performed on 19 burnt flints the late dates obtained for the stratigraphic layers bearing hominid remains confirm the evidence for the late presence of neanderthals in the levant the dates enable a more effective comparison of the lithic assemblages from amud cave with those of other contemporaneous sites and underline the variability within mousterian lithic industries at the end of the middle palaeolithic in the levant

morpho dynamics of the brahmaputra jamuna river bangladesh abstract the jamuna river is the downstream continuation of the brahmaputra in bangladesh it is one of the largest sand bed braided rivers in the world and every year it erodes thousand hectares of mainland floodplain rendering tens of thousands of people landless and or homeless understanding the morpho dynamics of this river and its responses to the various drivers of morphological change that act on it is essential to improving the livelihoods of millions of floodplain dwellers in bangladesh especially given the threats posed by climate change reliable data information and knowledge of river process are sparse and so progress in linking the impacts of multiple drivers including neo tectonics earthquakes large scale avulsions and engineering interventions to complex morphological responses depends on making best use of historical maps time series satellite images hydro morphological data expert judgment and local knowledge this paper draws on all these sources to chronicle the morphological evolution of the jamuna river since the avulsion that created it about 200 years ago and to establish temporal trends and spatial patterns in the changes that have characterized process response mechanisms in this fluvial system since then the understanding gained from these investigations then supports deeper analyses to explain how historical migration of the river westward has produced significant contrasts between left and right west bank material properties elucidate the relationships between discharge fluvial processes anabranch instability and floodplain erosion rates and identify causal links between drivers and morphological responses at a variety of time and space scales finally the new knowledge generated by the analyses developed herein are combined with existing conceptual and empirical process response models for the jamuna to predict possible future morphological adjustments in ways helpful in identifying appropriate strategies for climate change adaptation in bangladesh the enhanced knowledge gained from these historical and contemporary investigations may also be useful in assessing the impacts of natural and anthropogenic drivers on other large braided rivers

variable source depth acquisition for improved marine broadband seismic data in marine seismic data acquisition varying the source depth along a sail line gives diversity in sequential shot gather frequency spectra undesired alterations of the frequency spectra are created by the source ghost and by air gun bubble oscillations by deliberately varying the source depth along a sail line it is possible to obtain a seismic data set that will have energy more evenly distributed within the main frequency band of the source output this is obtained when data acquired with different source depths are stacked in imaging we formulated a simple inverse problem that seeks to find the optimal distribution of source depths over a sequential series of shots that shape the amplitude spectrum of the final image into a desired shape we assumed that the data are receiver side deghosted that designature could be applied to each shot gather and that the shot gathers could be redatumed to a common datum prior to imaging

an assessment of the degree to which landsat tm data can support the assessment of fluvial dynamics as revealed by changes in vegetation extent and channel position along a large river abstract recent research has demonstrated the capacity of remotely sensed data to enhance our understanding of interactions between fluvial processes and riparian vegetation multispectral landsat tm satellite data covering the last 30 years are now freely available and have the potential to support investigations at much broader spatial and temporal scales than previously possible this paper assesses the degree to which this data set can support the assessment of fluvial dynamics along a large gravel bed river the fiume tagliamento ne italy landsat tm scenes are used to determine spatio temporal trends in vegetation cover and channel position at six sites of contrasting environmental conditions along the river these trends are interpreted in combination with a number of additional hydrogeomorphological data sets before comparison with known biogeomorphological characteristics of the study sites as revealed by previous field research and analyses of higher resolution remotely sensed data sets the research highlights a number of limitations with landsat tm data that arise as a result of its relatively low spatial resolution including geomorphic feature definition and active tract delineation nevertheless the analysis demonstrates that landsat tm data can reveal a wealth of information that could support further biogeomorphological investigations in other large rivers

studying chert with electron spin resonance abstract archaeologists generally want to know how old their artifacts are and from where they came electron spin resonance esr is a tool for studying chert using radiation induced signals analogous to those used for thermoluminescence tl and optically stimulated luminescence osl dating as a dating technique it is well established for tooth enamel and shells and initial studies suggest it may be possible to date quartz sediments for this study however it is presently applicable only to heated chert work on samples from numerous sources has confirmed that heating chert is a complex process and both the duration and temperature of heating must fall within certain ranges in order to obtain datable samples both old world and new world material has been dated looking at these samples has also shown that variability among sources may permit proveniencing

on the use of multicomponent streamer recordings for reconstruction of pressure wavefields in the crossline direction three component measurements of particle motion would bring significant benefits to towed marine seismic data if processed in conjunction with the pressure data we show that particle velocity measurements can increase the effective nyquist wavenumber by a factor of two or three depending on how they are used a true multicomponent streamer would enable accurate data reconstruction in the crossline direction with cable separations for which pressure only data would be irrecoverably aliased we also show that conventional workflows aimed at reducing these aliasing effects such as moveout correction applied before interpolation are compatible with multicomponent measurements some benefits of velocity measurements for deghosting data are well known we outline how the new measurements might be used to address some long standing deghosting challenges of particular interest specifically we propose methods for recovering de ghosted data between streamers and for 3d deghosting of seismic data at the stream

planform channel dynamics of the lower colorado river 1976 2000 abstract in the past two decades major flood events have occurred on the lower colorado river a dramatic shift from the low flows and moderate floods associated with prior decades of river regulation this study uses repeat aerial photography and geographic information system analysis to examine the planform channel response of the upper colorado river delta limitrophe reach to this recently altered hydrology results indicate that channel contraction has been the dominant planform process in recent decades but periodic floods resulted in channel expansion 1981 1988 1997 2000 or likely reduced the channel contraction measured between successive aerial photographs 1976 1981 1988 1994 sinuosity adjustments were limited during the timeframe of the study range 1 31 to 1 38 but the channel did respond with large adjustments in channel width range 44 m to 355 m and changes in total mid channel bar area range 0 to 52 3 ha a channel probability model developed for this study provides a raster image of the channel changes and depicts areas modified to varying degrees by flood flows this historical study provides insight into how floods affect the channel system that provides the foundation for aquatic and riparian biodiversity this issue is of increasing relevance given growing international interest in rehabilitating the riparian and aquatic ecosystems of the colorado river delta through intentional flood flows

river islands change and impacting factors in the lower reaches of the yangtze river based on remote sensing abstract there are many developing river islands in the mawutong section of the yangtze river and their sizes change rapidly changes in eight river islands were studied using multi spectral scanner mss in 1979 and thematic maps tm in 1990 2001 2006 and 2009 the spectrum of typical objects in river islands was analyzed by isi921vf 256t field spectroradiometer bands combined and images interpreted by geometric correction subset images binarization processing convolution clump procedures and visual image interpretation a number of factors that were considered to influence the evolution of river islands were analyzed they include annual runoff annual sediment and soil particle composition of river islands the results show that 1 the isi921vf 256t field spectroradiometer can help to identify the correct spectrum of typical objects in river islands hence the selected bands three visible and one near infrared can be used to extract the variation of river islands area based on digital image processing and visual image interpretation 2 in general the eight river islands lengthened in 1979 2006 at various rates with the highest rate during 2001 2006 their sizes decreased rapidly in 2006 2009 except for two river islands 3 erosion and sediment deposition are two major physical processes that influence the evolution of river islands as no significant trend of annual total runoff in 1953 2010 was detected it is likely that the construction of large reservoirs upstream and hence the runoff dynamics and sediment loads in this region have more impact on the changes of river islands than do climate changes

deterministic estimation of a wavelet using impedance type technique a new deterministic technique for estimating a wavelet suggested by loewenthal and jakubowicz requires measurement of both pressure and vertical particle velocity through construction of the impedance function a deterministic estimation of the wavelet and the reflectivity can be obtained this idea is tested for a one dimensional model the test is carried out by forming a synthetic seismogram of both pressure and particle velocity and checking the formulas for obtaining the estimated wavelet under noisy conditions

river channel planform change software for historical analysis abstract er mapper an image processing system was used to manipulate scanned maps plans and aerial photographs to enable detailed analysis of historical river channel planform change the er mapper package offers the opportunity to spatially reference each item of planform data into the same scale and co ordinate space as a base map using a warping algorithm and operator selected ground control points once all the data are in the same co ordinate space and at the same scale a given point can be returned to over time and a number of indices can be easily calculated to examine past channel behaviour here lateral shift channel width sinuosity and area of sedimentation within the reach were used as the maps and aerial photographs themselves are used the errors associated with digitising vectors are avoided and a more flexible approach towards analysis and the identification of important indices can be adopted at the outset results obtained for the cleekhimin burn a site in southern scotland are briefly presented and discussed and the advantages of the package and the limitations of the historical database are also outlined

characterisation of monzogranitic batholiths as a supply source for heritage construction in the northwest of madrid abstract the church of the assumption of our lady in valdemorillo madrid spain is almost entirely built with granitoids the studies and analyses were focused on the oldest part of the building ghosts corner which will be restored and rehabilitated in the near future homogeneous monzogranite is the predominant granitoid used in the ghosts corner followed by granitic porphyry porphyrytic monzogranite gneiss and leucogranite the original quarries that supplied homogeneous monzogranites for the first construction stages correspond to blocks present in the monument s surroundings quarries that supplied the granitic porphyries correspond to the dykes located to east southeast of valdemorillo which are oriented n s in relation to their intrusion direction the combined use of ultrasonic velocity and schmidt hammer techniques allowed first selection of the most representative blocks and ashlars for sampling this reduced sampling to a minimum but yielded representative results for the whole building second the combined values were used to compare results for the building stones of the church to rocks from the surrounding quarries stones from the building showed lower ultrasonic and schmidt hammer values and higher porosity and water saturation values compared to the original quarry rocks the anisotropy indices are directly related to the decay processes in the stone spalling of homogeneous monzogranite and grain disintegration in granitic porphyries finally the methods applied are inexpensive easy to use and non destructive techniques very advisable properties when working with built heritage

new datings of amudian layers at qesem cave israel results of tl applied to burnt flints and esr u series to teeth abstract because only a few radiometric data are actually available the chronology of the amudian a blade dominated industry of the acheulo yabrudian cultural complex aycc of the late lower paleolithic in the levant is still not well constrained qesem cave offers the opportunity to enhance our knowledge of the chronological position of this industry which is unique to the levant the qesem amudian bearing layers yielded also human remains showing affinities with those of modern populations recovered in the middle paleolithic sites of skhul and qafzeh the results presented here are the first attempt to apply the tl and esr u series dating methods at this site and these methods yielded results which are generally in agreement they support a time interval of hominid bearing occupation of the areas of the cave where amudian lithic artifacts were recovered during mis 8 and likely 9 for the deep pit area and during mis 8 and possibly 7 for the upper part of the sequence square k 10 and the eastern microfauna bearing area an older occupation of the cave is also conceivable on the base of two dating results mis 11

the quartzite problem revisited abstract a review of past terminology and previous petrological studies suggests that quartzite should be classified descriptively as both a sedimentary and a metamorphic rock quartzite is identified in the field as a quartz rich rock exclusive of chert and vein quartz that is exceptionally hard and when broken by a rock hammer fractures irregularly through both grains and cement where present to form an irregular or conchoidal fracture surface quartzite is differentiated from quartzose sandstone arenite which is softer and fractures around individual grains and from chert and vein quartz by a bright vitreous luster quartzite is classified further on the basis of microscopic features into orthoquartzite and metaquartzite by the presence of clastic and metamorphic microtextures respectively low grade medium grade and high grade subtypes of metaquartzite are differentiated by mortar foam and porphyroblastic microtextures respectively composition is not used as a criterion for classifica

the role of the rocky mountains in the peopling of north america abstract this paper argues that the rocky mountains played a significantly more important role in the process of the peopling of the new world than archaeologists have traditionally recognized although first americans did not reach the rockies before they set foot in any other new world region they could not have regardless of their point of entry by clovis time evidence suggests that clovis people knew the rocky mountain landscape intimately archaeologists should have long anticipated this given the many resources the rocky mountains offer that adjacent albeit archaeologically better known regions such as the plains and some parts of the far west do not at least not as ubiquitously these include plentiful water in the form of streams lakes snowpack and glaciers high quality sources of obsidian chert quartzite and other knappable stone and a vertically oriented landscape that maximizes floral and faunal diversity within comparatively condensed space two other non economic characteristics likely contributed significantly to the appeal of the rocky mountains to some first americans the power and sanctity nearly all humans attribute to mountains and the seemingly little recognized fact that northeast asian upper paleolithic people who populated the new world during the terminal pleistocene occupied mountainous landscapes for some 45 000 years prior to their departure for many first americans mountains not the flat windswept tundra of siberian stereotypes had always been home evidence for the familiarity of clovis groups with the rocky mountain landscapes comes principally from three clovis caches anzick fenn and mahaffy all three caches are located in the rockies collectively contain artifacts made from ten of the highest quality stone raw materials available in the southern central and northern rockies and at least one of the caches accompanies the burial of a young child who appears to have been interred intentionally on a prominent and likely sacred landform in a mountain valley bringing the paper s argument full circle that same child s genetic profile shows a direct link to that of another youngster buried thousands of years earlier at the late glacial maximum mal ta site in the mountainous trans baikal region of siberia

sampling for provenance tailings from prehistoric stone quarries in the south pacific stone is a principal component in archaeological assemblages across the pacific it provided a major element in architecture used as trade goods and was fashioned into implements and ornaments monolithic monuments statues money and emblematic symbols of victory status and ethnicity in short stone is a pervasive element in the economic social and political fabric of pacific cultural traditions however provenance of rock quarries the source of this raw material has received limited attention in oceania provenance studies have been sidestepped or short changed in the rush to analyse artifactual materials here we establish a foundation for more robust provenance studies and field sampling strategies through a discussion of 1 quarry identification and 2 sampling within prospective sources a model of quarry identification sampling and characterization is drawn from work on rapa nui easter island and the fundamental precepts are outlined for future sampling experiments and provenance work in stone quarries generally

channel planform geometry and slopes from freely available high spatial resolution imagery and dem fusion implications for channel width scalings erosion proxies and fluvial signatures in tectonically active landscapes article i nfo the rapid expansion of high spatial resolution optical sensors and imagery over the last decade presents ex ceptional opportunities for quantifying visible attributes of geomorphic systems in this study we detail a simple robust methodology changeom to extract continuous channel width and centerline datasets for single thread channels using freely available high spatial resolution imagery currently available in google earth and bing maps comparisons with a global dataset of field and lidar derived channel widths indicate minimal errors associated with the imagery and changeom methodology b1 overall while examples from the goriganga river indian himalaya and the yakima river wa usa emphasize the benefit of em pirical width values over established channel width scalings in deciphering fluvial responses to complex landscape forcings in tectonically active regions additionally accurate centerline delineation from the changeom methodology provides improved sinuosity measurements and when fused with coarse resolution digital elevation models dems removes along profile shortening and coincident increases in reach scale channel slope lastly comparisons of aster gdem v2 srtm v4 1 and lidar channel profiles extracted in moderate to high relief regions demonstrate the inferiority of the aster gdem for channel slope calcula tions despite the apparent spatial resolution advantages 9 the methodology presented here will facili tate new discoveries in the fluvial environment that have historically been difficult due to access and imagery resolution issues and provide greater perspective on channel signatures and responses to a host of landscape forcings especially in tectonically active bedrock and lower order drainage systems

integrating subsurface stratigraphic records with satellite images to investigate channel change and bar evolution a case study of the padma river bangladesh landsat data and stratigraphic records were employed to determine channel changes and bar evolution of a selected reach of the padma river in bangladesh analysis of multi temporal images showed that the selected reach of the padma river has undergone significant morphological changes since 1973 the mean width of the river has almost doubled having increased from 5458 m in 1973 to 10 638 m in 2014 bank erosion totalling 281 km2 was more than double the accretion 123 km2 and the left bank experienced higher levels of erosion than the right bank analysis of the stratigraphy of the bar head middle and tail sections revealed that erosion occurred in the head section but that the middle section seemed to be stable whereas accretion was estimated to be high in the tail section of the bar sedimentary facies analysis indicated that bar evolution is largely influenced by the variation of both water and sediment flows as bar areas tend to accrete substantially following large floods however the erosion accretion process of both bars and river banks appeared to be stable during the periods when the river experiences no major flooding the relationship between bank erosion and bar area expansion showed a moderately positive correlation r2 0 64 p 0 016 while a strong correlation was observed r2 0 80 p 0 008 between channel width and area of the bar suggesting that river width is highly influenced by bank erosion this implies that the growth of bars within the reach is largely determined by materials flowing from bank failure

petrology and geochemistry of chert on the marginal zone of yangtze platform western hunan south china during the ediacaran cambrian transition the ediacaran cambrian transition was one of the most critical intervals in earth history during this interval widespread chert was precipitated commonly as a stratal wedge in carbonates along the southern margin of the yangtze platform south china the chert wedge passes into a full chert succession further basinward to the south east four lithotypes of chert are identified across the marginal zone in western hunan mounded vein brecciated and bedded chert the mounded chert is characterized by irregular to digitiform internal fabrics generally with abundant original vesicles and or channels that mostly are lined by botryoidal chalcedony cements with minor quartz and barite crystals the host chert or matrix of these mounds is dominated by amorphous cryptocrystalline silica commonly disseminated with pyrite the vein chert with minor quartz locally generally cross cuts the overlying dolostone and chert horizons and terminates under the mounded and or bedded chert bodies the brecciated chert commonly occurs as splayed intrusions or funnel shaped wedges and cross cuts the topmost dolostones the bedded chert the most common type generally is thin to medium bedded and laminated locally it is composed of amorphous silica with minor amounts of black lumps microthermometry of fluid inclusions from vein and void lining minerals mainly quartz and barite revealed homogenization temperatures from 120 to 180 c for the trapped primary fluids compositionally these chert deposits generally are pure with sio2 92 wt and only minor fe2o3 and al2o3 contents most of which show positive europium anomalies in rare earth element patterns especially for the mounded chert all these data suggest that the marginal zone chert deposits resulted from a low temperature silica rich hydrothermal system in which the mounded chert was precipitated around the releasing vents i e as silica chimneys the vein and splayed brecciated chert however was formed along the syndepositional fault fracture conduits that linked downward while the bedded chert was precipitated in the quieter water column from the fallout of hydrothermal plumes onto the sea floor these petrological and geochemical data provide compelling evidence and a new clue to the understanding of the extensive silica precipitation rapid tectonodepositional and oceanic changes during the ediacaran cambrian transition in south china

la icp ms analysis of quartzite from the upper gunnison basin colorado we report the results of la icp ms analysis of 402 quartzite samples representing 48 collection loci in the upper gunnison basin ugb colorado and determine the extent to which the sources can be geochemically discriminated from one another using this non destructive technique the ability to differentiate among the sources would open the door to provenance studies of the quartzite chipped stone tools and debitage that constitute 95 or more of most of the 3000 plus prehistoric site assemblages documented in the ugb our samples represent prehistorically quarried and non quarried quartzite sources including outcrop primary and gravel secondary deposits the results reveal spatial and chronological trends in quartzite elemental composition that can be exploited for provenance determinations of quartzite artifacts from ugb sites albeit using an assemblage based sourcing strategy that differs from the familiar approach of matching obsidian artifacts to their statistically likeliest geological source we offer a preliminary version of a sourcing protocol for ugb quartzite

the significance of large sediment supply active tectonism and eustasy on margin sequence development late quaternary stratigraphy and evolution of the ganges brahmaputra delta abstract borehole data from the ganges brahmaputra delta system unveil an intriguing late quaternary history controlled by immense sediment discharge tectonics and eustasy sea level first intersected a major portion of the lowstand surface 10 000 11 000 cal yr bp marking the onset of sediment trapping and delta growth despite rapid sea level rise 1 cm yr sediment load was sufficient to maintain relative shoreline stability during this time by 7000 cal yr bp accommodation was quickly infilled with slowed sea level rise leading to upstream channel migration and widespread dispersal of sands this forced coastal progradation along the western delta front where the ganges was situated and much of the river s fine grained discharge bypassed the subaerial delta and formed a prograding deltaic clinoform on the shelf concurrently brahmaputra sediments were sequestered to an inland tectonic basin thus starving the adjacent shoreline and leading to transgression along the eastern delta by 5000 cal yr bp the two rivers had migrated or changed course to discharge along the eastern delta shoreline which began to prograde into what is now the modern river mouth estuary present delta configuration appears to have developed by 3000 cal yr bp evolution of the tectonically active ganges brahmaputra g b system reveals important similarities and differences with other deltas overall facies succession follows that of basic models progressing from an alluvial valley to coastal marine delta front to a prograding subaerial delta plain however the timing thickness and controls of these deposits differ immense sediment discharge from the ganges and brahmaputra rivers allowed initial delta growth 2000 3000 yr earlier than the global average despite debouching onto a canyon incised high energy margin subsequently a thick 50 m transgressive systems tract was formed during the early holocene phase of delta aggradation contrasting with extensive shoreline retreat documented along most margins highstand progradation of coastal and shelf sequences ensued by the middle holocene but subsiding inland basins also favored accumulation of a thick to 40 m highstand sequence in the lower floodplains unlike many other delta systems subsidence in the subaerial g b delta is not dominated by compaction but rather by plate driven tectonic processes that generate rates up to 4 mm year overall the huge sediment load tectonic subsidence major seismic events and a nearshore canyon system have led to widespread sediment dispersal and sequence formation across the subaerial delta shelf and deep sea bengal fan throughout the late quaternary

is it optimal to tow air guns shallow to enhance low frequencies abstractin marine seismic acquisition it used to be commonly accepted that it is optimal to tow the source deep to enhance the low frequency content in the seismic data however mayne and quay found in 1971 that the low frequency response of air guns actually improves as the source depth decreases we evaluated a simple ad hoc theory that demonstrates that two effects are counteracting each other the free surface effect favors deep towed sources whereas the bubble time period increasing with decreasing source depth favors shallower tow depths from a fjord test we found that combining several source depths in an air gun array might flatten and improve the low frequency part of the source spectrum the experiment confirms that various source depths result in local characteristic maxima in the low frequency spectrum corresponding to the bubble time period of the air gun

assessing morphological changes of the ganges river using satellite images abstract using eight dry season satellite images of landsat mss 1973 1984 landsat tm 1993 2003 and irs liss 2009 this study assessed morphological changes of the ganges river within bangladesh as a typical alluvial river morphological changes of the ganges river had been a common phenomenon in the 1973 2009 study period with its morphologically dynamic nature the ganges river had undergone considerable changes in its river banks and its vegetated islands the bankline movement rates m y and erosion accretion rates ha y of the river were analyzed under four time periods 1973 1984 1984 1993 1993 2003 and 2003 2009 the results indicate that both the left and the right banks of ganges have changed significantly due to varying erosion and accretion rates that had occurred on a whole the left bank was more prone to accretion while the right bank to erosion the magnitude of bank erosion along the ganges river is closely related to the erodibility of riverbank materials which vary spatially in 1973 1984 the average river width and the overall islands area had decreased considerably due to a net river bank accretion which resulted in an increase of 6790 ha of land area however afterwards both river width and islands area continue to increase to the end of this study period 2009 because of a net erosion loss of 18 830 ha of land furthermore from 1984 to 2009 the sinuosity of ganges had generally increased and was related to increased river width caused by a net bank erosion compared to other major rivers ganges has a very high erosion rate probably because its river banks are primarily composed of highly erodible materials and its high discharge rate especially during the monsoon season

riverbank migration and island dynamics of the braided jamuna river of the ganges brahmaputra basin using multi temporal landsat images as one of the largest braided rivers in the world the jamuna river jm of the lower brahmaputra regularly undergoes significant erosion causing major bankline migration making thousands of families homeless and sizeable land loss every year e g the dynamic nature of jamuna causes great suffering to the people living along its course and on its islands therefore gaining a better understanding of the river s behavior should contribute to mitigate these sufferings and also to reduce the possible damage of the river to public infrastructure in this study using thirteen selected images of landsat mss and tm acquired from 1973 to 2003 the riverbank migration patterns and island dynamics of jm resulted from accretion erosion processes for 30 years were investigated for short term analysis the migration rate from one landsat image to the next is estimated for long term analysis the migration rates are based on the difference between the 1973 image as the reference and subsequent images for the short term long term analysis the average erosion and accretion rates are 227 and 271 m y 90 and 104 m y on the left bank and 187 and 148 m y 75 and 50 m y on the right bank of jamuna respectively because of human interventions and the averaging effect of erosion and accretion the long term migration rate is lower than that of the short term migration rate on both banks the short term rate of accretion erosion on the left right bank follows the general pattern of river bank migration while the accretion erosion of the right left bank does not follow such a pattern on the other hand the long term erosion and accretion processes for both banks partly follow the general pattern of river bank migrations from one flood to another large islands tend to be more stable with little changes but smaller islands underwent more changes from results obtained from analyzing multi temporal landsat images this study provides new and accurate information about the riverbank migration of jm