floodplain aggradation and pedogenesis in a semiarid environment alluvial valley fills in the upper republican river basin southwestern nebraska provide evidence for processes of aggradation and pedogenesis on semiarid cut and fill floodplains sheetflow deposition on unchanneled valley floors represents an important mechanism of valley aggradation sheetflow deposits contain parallel to sub parallel laminae and discontinuous lobate sedimentary structures rates of sediment deposition on cut and fill floodplains strongly determine the degree to which pedogenic features develop within aggrading alluvium three pedofacies common to semiarid alluvial deposits correspond with increasing aggradation rates 1 cumulic soils 2 multiple buried soils and 3 no pedogenic features radiocarbon age determinations from alluvial fills indicate that floodplain aggradation greater than approximately 0 5 cm year 1 limits soil formation this represents a threshold rate of pedogenic assimilation floodplain soils formed under aggradation rates lower than this exhibit a strong positive relationship between aggradation rate and total caco3 percent and a negative relationship between aggradation rate and organic carbon percent recognizing the associations between pedogenic sedimentologic features and floodplain aggradation rates can help interpret past rates of sediment transport storage and deposition

groundwater recharge history and hydrogeochemical evolution in the minqin basin north west china the minqin basin is a type area for examining stress on groundwater resources in the gobi desert and has been investigated here using a combination of isotopic noble gas and chemical indicators the basin is composed of clastic sediments of widely differing grain size and during the past half century over 10 000 boreholes have been drilled with a groundwater decline of around 1 m a 1 modern diffuse recharge is unlikely to exceed 3 mm a 1 as determined using unsaturated zone profiles and cl mass balance a small component of modern 50 a groundwater is identified in parts of the basin from 3h 3he data probably from irrigation returns a clear distinction is found between modern waters with median 18o values of 6 5 0 5 and most groundwaters in the basin with more depleted isotopic signatures radiocarbon values as pmc range from 0 6 to 85 modern but it is difficult to assign absolute ages to these although a value of 20 modern c probably represents the late pleistocene to holocene transition the 13c compositions remain near constant throughout the basin median value of 8 1 13c and indicate that carbonate reactions are unimportant and also that little reaction takes place there is a smooth decrease in 14c activity accompanied by a parallel increase in 4he accumulations from s n across the basin which define the occurrence of a regional flow system noble gas temperatures indicate recharge temperatures of about 5 6 c for late pleistocene samples which is some 2 3 c cooler than the modern mean annual air temperature and the recharge temperature obtained from several holocene samples groundwaters in the minqin basin have salinities generally below 1 g l and are aerobic containing low fe but elevated concentrations of u cr and se mean values of 27 5 5 8 and 5 3 g l 1 respectively nitrate is present at baseline concentrations of around 2 mg l 1 but there is little evidence of impact of high no3 from irrigation returns strontium isotope and major ion ratios suggest that silicate reactions predominate in the aquifer the results have important implications for groundwater management in the minqin and other water stressed basins in nw china a region so far destined for rapid development the large proportion of the water being used at present is in effect being mined and significant changes are urgently needed in water use strategy

channel fill and sheet flood facies sequences in the ephemeral terminal river gash kassala sudan abstract detailed facies analysis of the river gash fluvial sediments on two dimensional profiles across and along the main channel has revealed a number of facies and two distinct types of sequences channel fill and sheet flood sequences it seems that each sequence type is produced by specific depositional event and both sequences represent two end members for suite of mixed sequences the facies and sequences show rapid lateral variability and they merge and interfinger with each other they also show partial to complete modification due to subsequent floods and stage variation it seems that the thick sediments of the river gash in the kassala area were produced in two phases first by braided channel aggradation and lateral migration second by both channelized and unchannelized sheet flood deposition deposits of these two phases contribute to the sediments of the present day gash fluvial basin in the kassala area the gash sediments show some similarities and differences to those of ephemeral and low sinuosity braided streams the predominance of sheet flood deposits is consistent with the ephemeral flashy high flow regime in the river gash the non conformity of the river gash depositional style with the braided model of fluvial deposition may be due to this semi arid terminal flashy character which has control on the depositional processes and patterns

composition and architecture of braided and sheetflood dominated ephemeral fluvial strata in the cambrian ordovician potsdam group a case example of the morphodynamics of early phanerozoic fluvial systems and climate change abstract two fluvial facies associations braided and ephemeral fluvial are recognized in strata of the cambrian ordovician potsdam group in the ottawa embayment and quebec basin in northeastern north america braided fluvial sedimentation was dominated by the migration of coarse grained sandy dunes and rare unit bars and local gravels that built up low relief 0 4 5 m thick downstream accreting compound bars in very wide and shallow braided channels rare meter scale confluence scours incision and filling of decimeter thick bypass channels and thin 7 cm overbank deposition also occurred ephemeral fluvial sedimentation was dominated by the progradation of lobate terminal splays most of which were deflated and or reworked into thin 10 95 cm sheets by eolian processes during the long recurrence intervals between floods these strata were locally incised by rare 0 3 1 9 m thick scour filling high energy supercritical bedform strata and decimeter thick bypass channels both braided and ephemeral fluvial deposits consist of meter scale stacked high order stratal units separated by horizontal laterally extensive surfaces recording the recurring buildup avulsion and finally abandonment of channel belts in braided fluvial strata of the potsdam the dominance of thin 2 m elongated compound bars with low relief 5 bar margins and internal accretion surfaces 15 suggest that braided channels and in channel compound bars expanded laterally with negligible increase in flow depth during periods of increased discharge in the absence of bank stabilizing vegetation similar to other examples of the pre vegetated sheet braided style however in areas where bedrock topography inhibited the lateral expansion of channels thicker compound braid bars 1 2 3 5 m with higher relief accretion surfaces up to 35 like those observed in post silurian and modern systems preferentially formed in relatively deep channels ephemeral fluvial deposits here are similar to ephemeral examples throughout geologic history in that they mostly comprise poorly confined sheet like terminal splays that accumulated in topographic lows however compared to several post silurian examples strata in the potsdam exhibit considerably more eolian reworking of splays and preservation of supercritical bedform strata a manifestation of greater rates of surface water infiltration due to a lack of sheltering by rooted plants and propensity for unconfined flooding finally in the upper part of the potsdam two regional ephemeral fluvial units are interstratified with two braided fluvial units providing evidence for shifts in regional climate the sharp areally extensive surfaces that separate these fluvial systems are interpreted to approximate time lines and therein provide a means for relative and absolute chronostratigraphic correlation these changes are correlated with documented late cambrian to earliest ordovician global climate fluctuations with semiarid conditions and related ephemeral fluvial systems corresponding to global cooling events at ca 491 and 487 ma

fluvial processes and cyclicity in terminal fan deposits an example from the late devonian of southwest ireland abstract the gun point formation is a sandstone dominated sequence approximately 1 5 2 5 km thick which forms part of a major 6 km late devonian alluvial basin fill succession in southwest ireland it is interpreted as the deposits of a southerly flowing terminal fan system which operated under a semi arid climate the proximal zone was characterized by low sinuosity gravelly feeder channels which passed downstream into a medial zone dominated by a sandy braidplain further south in the distal zone phases of high energy flood activity were centred on transient low sinuosity ephemeral channels and were separated by more quiescent periods of shallow sheetflooding subaerial exposure and non deposition sedimentary parameters such as set thickness coset thickness channel sand body density and maximum sand body thickness all exhibit regular cyclic fluctuations with a periodicity of 160 180 m the cycles are interpreted as evidence of regular discharge variations which may have been a response to the 412 ka orbital eccentricity cycle a second periodicity of approximately 700 m has also been detected and is thought to reflect long term variations in basin subsidence

hydrogeochemical and isotopic evidence of groundwater salinization in a coastal aquifer a case study in jeju volcanic island korea abstract in order to identify the origin of saline groundwater in the eastern part of jeju volcanic island korea a hydrogeochemical and isotopic study has been carried out for 18 observation wells located in east and southeast coastal regions the total dissolved solid contents of groundwaters are highly variable 77 21 782 mg l oxygen hydrogen sulfur and strontium isotopic data clearly show that the saline water results from mixing of groundwater with seawater strontium isotopic compositions and br cl and i cl ratios strongly suggest that the source of salinity is modern seawater intrusion hydrogeochemical characteristics based on bivariate diagrams of major and minor ions show that changes in the chemical composition of groundwater are mainly controlled by the salinization process followed by cation exchange reactions the highly permeable aquifers at the east coastal region are characterized by low hydraulic gradient and discharge rate and high hydraulic conductivity as compared with other regions these properties enhance the salinization of groundwater observed in the study area based on the cl br and 18 o data seawater was determined to have intruded inland some 2 5 km from the coastline considering the poor correlation of sampling depth and cl concentrations observed the position of seawater freshwater interface is not uniformly distributed in the study area due to heterogeneities of the basaltic aquifers

a preliminary assessment of hydrogeological features and selected anthropogenic impacts on an alluvial fan aquifer system in greece an investigation was carried out to delineate the hydrogeologic framework and to understand groundwater quality of the kompsatos river fan aquifer system northeastern greece as well as to assess environmental impact induced by human activities as groundwater is the only major source of water in this area it is important to know the effect of geological formations and anthropogenic activities on groundwater chemistry and environment a thorough hydrogeological study was performed during the period 2004 2007 the differential river gauging method was used for estimating the volume of water leaking from or discharging into the river groundwater samples were collected from 89 monitoring wells during the summer period of 2007 and analyzed for major ions and trace elements a potential reservoir of groundwater is formed within the kompsatos river fan the aquifer system kompsatos river interaction is the outstanding feature of this area ca mg hco3 so4 is the dominant water type as a result of dissolving carbonate salts b ba mn li sr and zn are the most abundant trace elements in groundwater both the major ion chemistry and trace element enrichment of the groundwater are controlled by mineral dissolution and water rock interaction nitrate contamination of groundwater is related to agricultural practices an improperly constructed drainage system led locally to salinization of groundwater channelization has caused considerable disruption to the river ecosystem the eventual construction of a dam on the river will adversely affect the environment and the aquifer system the lack of managerial policy for water is putting environmental resources and water supply in jeopardy

architecture of pre vegetation sandy braided perennial and ephemeral river deposits in the paleoproterozoic athabasca group northern saskatchewan canada as indicators of precambrian fluvial style abstract the late paleoproterozoic athabasca basin contains more than 1 5 km of predominantly sandy strata most of which are of braided fluvial origin in the eastern part of the basin at mcclean lake sandstones and minor conglomerates of the read formation at the base of the succession are preserved within a steep walled valley system they consist predominantly of meter scale sheet elements characterized by massive and flat laminated fine to very coarse grained sandstone with minor discontinuous cobble and boulder conglomerate along lower set boundaries these are interpreted as sheet flood and stream flood deposits of a terminal dry land system deposited in an arid climatic setting analysis of closely spaced drill core indicates that late stage run off was confined to small shallow channels typically only a few tens of meters wide and a few meters deep overlying strata of the bird member of the manitou falls formation are predominantly coarse to very coarse grained sandstones with abundant small scale cross stratification and minor granule and small pebble conglomerate at mcclean lake these appear to have been deposited as sheet elements by semi ephemeral to perennial braided rivers under more humid conditions at key lake 160 km to the southwest architectural analysis of a 184 m wide section indicates that at least part of the bird member was deposited in deeper sandy braided rivers characterized by seasonally varied flow the closest modern analogue is the south saskatchewan river in which large simple flow transverse bedforms become exposed and dissected during falling stage and act as nuclei for sand flat development the presence of numerous low relief 4th order surfaces suggests continued reworking of bar tops during rising stage the incremental character of downstream accretionary elements suggests periodic migration of barforms during peak flood stages separated by periods of low flow this indicates similarities with modern perennial braided systems and is counter to the idea that all pre devonian fluvial systems should consist of stacked sheets formed by individual flood events thin gravel layers accumulated as lags on fourth order surfaces with discontinuous mud layers suggesting deposition within temporary ponds in channel thalwegs after major floods strata in overlying units indicate a return to semi perennial conditions

terminal fans and the ganga plain tectonism a study of neotectonism and segmentation episodes of the indo gangetic foreland basin india abstract the study of spatial and temporal distribution of holocene terminal inland fans in the indo gangetic foreland basin suggests that the segmentation of the basin was initiated at 9 3 ka and continued up to 0 75 ka in three distinct episodes the earliest episode 9 3 7 3 ka was exclusively confined in the upper gangetic plain this episode covers 29 of total time span and contributes 13 of total faults including their reactivations development of six faults associated with terminal fans having large age gaps indicate relatively slow rate of faulting activities in the early holocene the second faulting episode was started at 6 4 ka and continued up to 2 3 ka covering 60 time of the total time span and contributed 69 of total faults including their reactivations though in most of the time the faulting events were confined in the upper gangetic plain but development of few faults in the middle gangetic plain in the middle of this episode shows a transitional shift of tectonic front from the upper to the middle gangetic plain the third faulting episode 1 5 0 75 ka is mainly confined in the middle gangetic plain this episode covers 11 time of the total time span and contributes 18 of faults out of the eight faults seven of them are in the middle gangetic plains though these three episodes have contributed in segmentation of the gangetic plains but the second episode was responsible for major segmentation of the region two major tectonically stable periods 7 3 6 4 ka and 2 3 1 5 ka and three minor periods in duration of 0 5 ka have been observed in the region episodic development of faults in individual tectonic blocks indicates that the stress distribution along the plains is non uniform which can also be correlated to the adjacent corresponding segments of the himalayan tectonics it has been observed that in each fault bounded block the faulting events start slowly and later becomes more frequent previous work pointed out four tectonically active episodes between the ghaghara and kosi rivers with the oldest faulting event at 7 89 ka however the region west of it i e between the ghaghara and ghaggar rivers which includes rest of the upper gangetic plain shows that neotectonic activities are earlier than 7 89 ka the oldest faulting event observed by previous study the youngest faulting episode of the present study coincides with that of previous study and suggests that the region between the gandak and kosi rivers is tectonically most active at present the tectonically stable periods pointed out in the previous study between the ghaghara kosi region is occupied by the faulting events in the upper gangetic plains hence instead of four tectonically active episodes the whole ganga plain witnesses three segmentation episodes with two major intervening stable periods the change of orientation of the faults in the plain may be correlated to directional change of indian plate motion differential convergence and upliftment rates along the himalayan front and the spatial extension of subsurface precambrian basement ridges into the plains

using h and o isotopic data for estimating the relative contributions of rainy and dry season precipitation to groundwater example from cheju island korea abstract a comparison of deuterium excess or d values of precipitation and groundwater at cheju island korea indicates that unlike in many temperate climates precipitation during the whole year contributes to groundwater recharge this in turn suggests that evapotranspiration effects are minimal consistent with the fact that the island contains highly permeable volcanic rocks overlain by thin soils this hypothesis is contrary to current water budget models that ascribe a significant role to evapotranspiration processes three coastal springs and several streams and ponds throughout the island have enriched 18 o and d values that plot off the local meteoric water line and have relatively high cl concentrations this relationship is suggestive of seawater mixing for the coastal springs and evaporation for the streams and ponds this database thus provides a useful means for evaluation of groundwater resources of the island

hydrogeochemical and isotopic characterization of groundwater salinization in the bangkok aquifer system thailand the deterioration of groundwater quality particularly due to salinization because of the overexploitation of groundwater in the lower central plain of thailand remains a major concern with increasing demand for water there is a growing need for sustainable management of the resource which would benefit from an improved understanding of the sources of chloride contamination thus a hydrochemical and isotopic study was carried out to chemically characterize groundwater and to investigate possible sources of salinization and in particular of chloride contamination in the multi layered bangkok aquifer system groundwater samples were taken from four topmost aquifers bangkok phra pradaeng nakhon luang and nonthaburi additionally short term rainwater sampling as well as river and seawater sampling was performed and later analyzed for ionic composition and stable water isotopes ionic and isotopic data indicate at least three different recharge sources for groundwater the major recharge source is rainwater the influence of seawater is limited to the coastal region and tidally influenced areas of the two main rivers chao phraya and tha chin bromide data also suggest the influence of saline water in deeper aquifers due to trapped water most importantly although the influence of seawater on groundwater is recognizable the surrounding geology contributes a significant number of dissolved ions detected in the groundwater

spatial characterization of the seawater upconing process in a coastal mediterranean aquifer plana de castellon spain evolution and controls in this contribution we describe the formation and evolution of the upconing process in a mediterranean coastal aquifer the study area has experienced severe salinization over the last 40 years because of intensive exploitation of groundwater we used historical and current records of piezometric levels and chloride concentrations to trace the development of the salinization of the aquifer we defined the 3d shape of the saline wedge from the spatial distribution of chloride concentrations and vertical well logs of electrical conductivity using monitoring network data upconing first appeared in the early 90s and has continued until the present day in this study we examined the intensity of the upconing process dry periods and the associated increases in pumping caused the advance of seawater intrusion the sharp reduction in groundwater withdrawals over the last 10 years has caused the saline wedge to move backwards although the ongoing pumping and the climate conditions mean that this retreat is quite slow

seawater inrush assessment based on hydrochemical analysis enhanced by hierarchy clustering in an undersea goldmine pit china seawater inrush is deadly to undersea mine and it is very important to accurately assess the connectivity between seawater and the mine pit with xinli gold mine area as a case study following the analysis of geological setting a detailed hydrogeological survey and sampling were conducted and conservative ions test of mine water samples was carried out in the laboratory furthermore the physical significances of ion concentration and ion ratios such as cl so42 cl and na cl were checked the test data analysis enhanced by the physical significance check and hierarchy clustering analysis was used to assess the overlying seawater inrush into the mine pit it was determined that the undersea rock masses in the xinli mine area bear high mineralization brine water the ore controlling fault gouge and a thin layer of clay in quaternary block the seepage of overlying seawater into the undersea mine pit to a great extent the mine water from surrounding rock of the northeast gopher drift is closer to seawater in hydrogeochemical features which indicates that the connectivity between the northeast of footwall of the ore controlling fault and seawater is relatively good and should be closely monitored in future production the mine water from the southwest gopher drift and crosscuts is similar to the brine salty water in chemical features drains the net reserves of brine salty water in bedrock fissures and will impose few impacts on production in the near future this approach is feasible and cost effective

distribution of palaeosols and deposits in the temporal evolution of a semiarid fluvial distributary system bauru group upper cretaceous se brazil abstract the stratigraphic and sedimentological knowledge of the bauru group upper cretaceous se brazil is still generally insufficient and controversial a sedimentological and palaeopedological study allowed to interpret the south eastern portion of the bauru group according to the model of a fluvial distributary system this work has two objectives 1 to include palaeosols in the interpretation of a fluvial distributary system and 2 to give detailed information on the sedimentological and stratigraphic features of the se portion of the bauru group in order to support biostratigraphical taphonomic and palaeoecological studies in the south eastern portion of the bauru group three genetic stratigraphic units were described and interpreted here informally called lower intermediate and upper units the lower unit is constituted of muddy sandstone salt flat deposits and sandstone sheet deltas deposits and is interpreted as a basinal part of a fluvial distributary system the intermediate unit is formed of very fine to fine grained sandstone filled ribbon channel and sandy sheet shaped beds suggesting a distal or medial portion of a fluvial distributary system the upper unit does not match with the present models of the fluvial distributary system because mostly constituted of moderately developed well drained medium to fine grained sandstone palaeosols which testify pauses of sedimentation to the order of 104 years preserved features of sedimentary structures suggest that the parent material was formed by occasional catastrophic unconfined flows this unit may represent the most distal portion of a fluvial distributary system generated by retrogradation of the alluvial system due to aridification of the climate the upper unit may be interpreted also as proximal portion of fluvial distributary system if considering the coarser grained and the well drained palaeosols however the absence of channel deposits makes this interpretation unconvincing

architectural elements and bounding surfaces in fluvial deposits anatomy of the kayenta formation lower jurassic southwest colorado abstract three well exposed outcrops in the kayenta formation lower jurassic near dove creek in southwestern colorado were studied using lateral profiles in order to test recent regarding architectural element analysis and the classification and interpretation of internal bounding surfaces examination of bounding surfaces within and between elements in the kayenta outcrops raises problems in applying the three fold classification of allen 1983 enlarging this classification to a six fold hierarchy permits the discrimination of surfaces intermediate between allen s second and third order types corresponding to the upper bounding surfaces of macroforms and internal erosional reactivation surfaces within the macroforms examples of the first five types of surface occur in the kayenta outcrops at dove creek the new classifications is offered as a general solution to the problem of description of complex three dimensional fluvial sandstone bodies the kayenta formation at dove creek consists of a multistorey sandstone body including the deposits of lateral and downstream accreted macroforms the storeys show no internal cyclicity neither within individual elements nor through the overall vertical thickness of the formation low paleocurrent variance indicates low sinuosity flow whereas macroform geometry and orientation suggest low to moderate sinuosity the many internal minor erosion surfaces draped with mud and followed by intraclast breccias imply frequent rapid stage fluctuation consistent with variable seasonal monsonal ephemmeral flow the results suggest a fluvial architecture similar to that of the south saskatchewan river through with a three dimensional geometry unlike that interpreted from surface studies of that river

quantification of groundwater seawater interaction in a coastal sandy aquifer system a study from panama sri lanka the panama coastal aquifer system is an important water resource in the southeast coast of sri lanka that provides adequate supplies of water for agriculture and domestic uses one of the biggest threats to these fragile aquifers is the sea water intrusion in this study recharging mechanism and geochemical evaluation of groundwater in the coastal sandy aquifer of panama were evaluated using chemical and stable isotope techniques thirty groundwater samples were collected and analyzed for their major ion concentrations and stable isotope ratios of oxygen 18o 16o and hydrogen d h all studied samples showed a ranking of major anions in the order cl hco 3 so 4 2 n no3 while cations showed a decreasing order of abundance with na ca2 mg2 k dominant groundwater hydrogeochemical types were na cl and mixed ca mg cl results of saturation index calculations indicate that the investigated groundwater body was mostly saturated with respect to calcite dolomite and gypsum in addition stable isotope and geochemical data suggest that fresh groundwater in the aquifer is recharged mainly by local precipitation with slight modification from evaporation and saline water intrusions isotope data suggest that mixing of salt water with freshwater occurs in aquifers which are located towards the lagoon since the communities in the study area depend entirely on groundwater an understanding of the hydrogeochemical characteristics of the aquifer system is extremely important for the better water resource management in the region

climatic and geomorphologic cycles in a semiarid distributive fluvial system upper cretaceous bauru group se brazil abstract studies of distributive fluvial systems and their preserved successions envisage the distribution and orientation of architectural elements to be primarily controlled by channels radiating outward from fan apices in many cases along an elongate basin margin conceptual models for such systems account for the downstream dynamics of the fluvial network but with limited consideration of temporal geomorphic variations resulting vertical organisation of architectural elements or of the interplay of factors controlling system dynamics to understand the external and internal architecture of distributive fluvial systems and the factors that influence their sequential facies organisation a sedimentary succession of the proximal portion of an upper cretaceous semiarid distributive fluvial system located at the north eastern margin of the bauru basin southeast brazil has been analysed in detail three fining and thinning upward fluvial sequences are identified forming an interval separated at the top and the bottom by two palaeosol profiles each sequence is formed of channel and floodplain deposits two types of channel deposits are identified one is composed of stacked sets of small scale dune deposits suggesting perennial and steady fluvial regime associated with more humid climate periods the other is composed of large scale sets indicative of flattened dunes associated with unsteady and fast changing fluvial flow formed in quasi supercritical flow regime conditions associated with drier climate periods the vertical alternation of these two types of channel deposits records the accumulation of a fluvial succession that responded to high frequency climate induced cyclic change in boundary conditions two palaeosol profiles at the top and at the bottom of the succession indicate temporary interruptions and cessation of the fluvial sedimentation likely related to avulsion of the fluvial belt thus the studied succession reveals high frequency climate induced allogenic sedimentary cycles that occur within a long period autogenic geomorphologic induced sedimentary cycle this work suggests that the internal architecture of the channel deposits can be used as a climate proxy and that climate and geomorphology act jointly as notable factors to control the vertical organisation of distributive fluvial systems

an experimental study on dynamic processes of ephemeral gully erosion in loess landscapes abstract ephemeral gully erosion is widespread on the loess plateau of china to provide theoretical support for constructing numerical models and soil water conservation planning the hydrodynamic characteristics of ephemeral gully flows were studied by laboratory experiments with a physical model we firstly concluded that with the influence of step slope pool or step pool terrain on the bottom of gully channels no obvious or consistent pattern changes were evident in the hydrodynamic parameters along the flow direction secondly the change of hydrodynamic parameters during erosion could be classified into an initially fast changing interval followed by a stable period and the initial adjustment period would become shorter with increasing slope and rainfall intensity thirdly ephemeral gully erosion flows were turbulent and changed frequently in space and time between supercritical and subcritical flows throughout the experiment the reynolds number fluctuated and increased with time with increasing rainfall intensity and gully slope the frequency of larger reynolds numbers increased in addition the froude number also fluctuated but decreased with time and the mean froude number eventually stabilized at 0 5 at different slope angles and rainfall intensities fourthly the distribution of erosional energy was influenced mainly by topography in loess slopes in the case of 20 slopes the inverse ratios of dissipation as soil erosion sediment transport and flow kinetic energy were relatively stable in time and space during ephemeral gully erosion moreover flow velocity shear stress the darcy weisbach friction factor and the manning coefficient were influenced by rainfall intensity to a lesser degree during erosion in the stable interval for 15 and 25 slopes shear stress the darcy weisbach friction factor and manning coefficient of ephemeral gully flow both increased with increasing rainfall intensity flow velocity on the 15 slope decreased initially then increased with increasing rainfall intensity but flow velocity on the 25 slope decreased with increasing rainfall intensity finally the regularity seen in hydrodynamic parameters of ephemeral gully flows occurred despite disturbance from lateral confluences gravity erosion of the channel bank and changes in terrain the sediment transport capacity of ephemeral gully flows increased with usp by a linear function r 0 64 n 99 p

sequence stratigraphy and marine to nonmarine facies architecture of foreland basin strata book cliffs utah u s a the desert member of the blackhawk formation and the castlegate sandstone in the book cliffs of utah and colorado were analyzed to develop a model of sequence stratigraphy and facies architecture in foreland basins stratal architecture of these rocks is controlled by two regionally extensive surfaces of incision and subaerial exposure interpreted as major sequence boundaries and at least six surfaces of incision and subaerial exposure with more limited lateral extent interpreted as minor sequence boundaries each sequence boundary is a regionally correlatable single surface major sequence boundaries can be traced from marine into proximal alluvial plain environments sequence boundaries have different physical expressions depending upon where in the basin they are observed strata beneath sequence boundaries are unrelated to strata above and time lines cannot be carried across these boundaries flooding surfaces called parasequence or parasequence set boundaries also exert an important control on facies architecture based on parasequence stacking patterns position of sequence boundaries and facies associations the desert member and castlegate sandstone have been divided into sequences with durations of 200 000 to 300 000 yr there are an order of magnitude more sequences in this interval than are predicted by the global sea level chart of haq et al 1988 the major sequences have been divided into the following systems tracts or sequence sets 1 grassy highstand sequence set below the desert sequence boundary named for the grassy member of the blackhawk formation 2 desert lowstand transgressive and highstand systems tracts between the desert and castlegate sequence boundaries 3 castlegate lowstand sequence set resting on the castlegate sequence boundary and 4 castlegate transgressive systems tract parasequence stacking patterns suggest that the grassy highstand sequence set and the desert highstand systems tract were deposited during a relative rise in baselevel the grassy highstand sequence set is punctuated by minor relative falls in baselevel both of these stratal units contain thick

spatial and temporal distribution of inland fans terminal fans between the ghaghara and kosi rivers indicate eastward shift of neotectonic activities along the himalayan front a study from parts of the upper and middle gangetic plains india abstract neotectonic deformation in the indo gangetic plains is primarily manifested by surface ruptures caused by both normal faults and thrust splays the topographic breaks along these faults provide suitable sites for the formation of inland fans terminal fans on the down thrown blocks as these depositional features invariably form along the faults contemporaneously or soon after faulting they have widely been used as potential geomorphic markers in mapping faults in the flat gangetic plains based on this association infrared stimulated luminescence irsl dating of the fans has successfully been used for dating the faulting episodes in the gangetic plains thus the spatial and temporal distribution of inland fans terminal fans suggests migration of faulting activities from west to east with time and successive faulting events occur over periods of several hundreds of years to 10 3 years in the present study the correlation of eighteen dated inland fans terminal fans aligned along the faults and using the surficial and buried soil profiles suggests four deformation episodes 7 89 7 30 ka 5 84 3 99 ka 3 18 2 73 ka and 1 41 0 75 ka in the region between the ghaghara and kosi rivers in the gangetic plains these deformation episodes were witnessed by the development and reactivation of the extensional normal faults transverse to the himalayan frontal thrust hft in the ghaghara rapti interfluve and the thrust splays parallel sub parallel to the hft in the gandak kosi interfan regions the rapti gandak region in the middle serves as a transition zone in between the interfluve and the interfan region and shows both types of fault development at different times six inland fans terminal fans in the ghaghara rapti interfluve were formed between 7 89 and 2 73 ka in three deformation faulting episodes two in each phase the broad age difference between those and strongly developed soils suggests the faulting activities to be less frequent in this region the fan building episodes in the gandak kosi interfan region started at 4 92 ka by the initiation of thrusting activities out of eight inland fans terminal fans five of them were formed during 1 41 0 75 ka in association with various thrust splays these depositional features are characterised by a narrow age gap and weak to no surface soils which indicate early burial by high sediment supply from frequent thrusting activities segments of the plains having a high low population of inland fans terminal fans of narrow broad age gaps and with relatively weakly strongly developed soils lie close to or opposite to the segments having the highest lowest rate of convergence and upliftment of the himalayas along the hft

late quaternary geology of the lower central plain thailand abstract the lower central plain or chao phraya plain located in the upper gulf of thailand has an average elevation of 2 m above the present mean sea level it is a fault bounded basin developed in the plio pleistocene epoch consequently the basin has been filled with quaternary sediment reaching a thickness of almost 2000 m of which only the upper 300 m is known the pleistocene deposits of the lower central plain represent a complex interplay of alluvial fluvial and deltaic environments of the chao phraya river and its tributaries the upper sequence of sand and stiff clay with iron oxide concretions on the surface was deposited in a fluviatile environment subjected to a regressive period in the late pleistocene the term chao phraya delta is used to define the landform where the chao phraya river interacted with marine processes as the sea level changed during the holocene transgression these strata indicated that the holocene sea reached its maximum height of 4 m above the present mean sea level around 6000 years b p from then on sea level fluctuated until it reached its present level around 1500 years b p this complex sea level history has caused the progradation of tidal flat and tide dominated delta deposits consisting of soft marine clay that covered the lower central plain to an average depth of 15 m in the bangkok area the soft marine clay or bangkok clay is the most important unit in the stratigraphic sequence in terms of land subsidence in the lower central plain evidence of coastal erosion is also considerable in the low tidal flat area on the west bank of the chao phraya river mouth and adjacent coast