a tsunami deposit at the cretaceous tertiary boundary in texas at sites near the brazos river texas an iridium anomaly and the paleontologic cretaceous tertiary boundary directly overlie a sandstone bed in which coarse grained sandstone with large clasts of mudstone and reworked carbonate nodules grades upward to wave ripple laminated very fine grained sandstone this bed is the only sandstone bed in a sequence of uppermost cretaceous to lowermost paleocene mudstone that records about 1 million years of quiet water deposition in midshelf to outer shelf depths conditions for depositing such a sandstone layer at these depths are most consistent with the occurrence of a tsunami about 50 to 100 meters high the most likely source for such a tsunami at the cretaceous tertiary boundary is a bolidewater impact

the role of midsummer urban aquifer recharge in stormflow generation using isotopic and chemical hydrograph separation techniques summary results dispute the traditional view that groundwater contribution to urban streams during storm events is too small to significantly influence stream flow rates the study used a two component hydrograph separation technique involving oxygen 18 and electrical conductivity to quantify event and pre event components of stream flow associated with a midsummer precipitation event in a highly urbanized formerly glaciated catchment isotopic separation results showed that only about 15 of the rainfall amount contributed to overland flow with groundwater accounting for 22 of the total stormflow elevated electrical conductivity values possibly associated with the flushing of urban contaminants during the storm suggested a slightly higher 30 groundwater contribution to total stormflow it was also demonstrated that nearly 6 of total rainfall contributed to aquifer recharge representing significant summer recharge in the urban catchment the findings are contrary to the prevailing assumption that stormflow in highly urban catchments is largely overland flow

soil moisture and groundwater responses to snowmelt on a drumlin sideslope abstract hillslope soil moisture and groundwater fluxes at a site in south central ontario were examined during the 1986 spring snowmelt near surface soil moisture was found to respond rapidly to the daily snowmelt cycle and a perched aquifer was formed in the latter stages of melt due to a progressive decrease in soil permeability with depth the delay between the initiation of snowmelt and the production of an extensive perched aquifer appears to have resulted from microscale variations in wetting behaviour induced by heterogeneity in soil texture and porosity subsequent additions of rainwater to the aquifer s capillary fringe produced an upward extension of phreatic conditions into more permeable near surface layers resulting in increased groundwater contributions from the hillslope previous studies indicate that saturation overland flow dominates the runoff response of catchments in this region during snowmelt the present results suggest that much of the return flow component of this runoff mechanism is produced by these transient perched aquifers this has implications for both hydrochemical studies and the use of environmental isotopes in investigations of snowmelt runoff

the crustal structure of the southern nain and makkovik provinces of labrador derived from refraction seismic data data from a refraction seismic profile parallel to the coast of labrador canada were used to determine the crustal structure across the boundary of the nain and makkovik provinces and to look for evidence for an offshore continuation of the mesoproterozoic nain plutonic suite nps seven seismometers recorded airgun shots along the 283 km long line p and s wave velocity models were developed from forward and inverse modeling of travel times the velocity model distinguishes three distinct zones in the saglek block of the nain province the crust is divided into three layers with p wave velocities between 5 8 and 6 9 km s farther to the south upper crustal velocities increase to 6 3 6 5 km s and the poisson s ratio increases from 0 24 to 0 27 this zone correlates with a gravity low that is interpreted to outline the offshore continuation of the nps the upper crustal velocities are intermediate between anorthositic and granitoid rock samples collected from the nps a lower crustal reflector is li

sedimentary features of the seismo turbidites lake biwa japan abstract seismo turbidite layers are deposited at the foot of the steep slope of the half graben in which lake biwa has accumulated sedimentary studies especially of grain size distribution of selected turbidites provide excellent information for clarifying the distinctive features of general seismo turbidites development of the two constituent sublayers lower sandy sublayer and upper silt sublayer lack or limited appearances of traction indicating structures and characteristic grain size distribution in the two constituent sublayers are most remarkable and significant the characteristic grain size distribution features are coarse tail grading in a relatively thick sandy sublayer exceptionally rapid distribution grading through the thin boundary interval between the two sublayers height increase and fluctuation of the silt mode and high clay content brief discussion was made on the causes of these sedimentary features the need and importance of further comparative studies of various turbidites known triggering forces are emphasized

new findings of bronze age homogenites in the ionian sea geodynamic implications for the mediterranean abstract holocene homogenites similar in character and stratigraphic position to those previously recorded in the ionian basin and related to the gigantic tsunami originating from santorini bronze age eruption are described from a core transect crossing the deformation front of the mediterranean ridge east of victor hensen seahill investigations on grain sizes and carbonate content carried out on three cores from three different areas of the ionian basin encompassing the bronze age homogenite revealed important similarities and some differences the most obvious difference concerns the carbonate content which is minimum at the base of the unit in a core close to the messina abyssal plain whereas it is maximum in cores from the western mediterranean and calabrian ridges characterized by the typical cobblestone topography a terrigenous versus pelagic nature of the components is documented and a distal versus local provenance is inferred homogenites are critically compared with unifites a type of re sediment recently described from the eastern mediterranean comparison includes in particular a source and sediment transport and b triggering mechanism a substantial difference exists between the sedimentation patterns of the ionian and levantine basins seaward of the calabrian and hellenic arcs in the latest quaternary and the difference contains a clear geodynamic message sedimentation rates increase from the late pleistocene to the holocene in the ionian basin whereas they decrease in the levantine basin the glacio eustatic signal is well expressed in the levantine basin where the source areas are situated consistently in the south or on a passive type aseismic continental margin north african margin in the ionian basin on the contrary the glacioeustatic signal is totally obscured by the strong tectonic signal from the active northern continental margin of the mediterranean

numerical simulation of floodplain hydrology despite the extensive research into hillslope and channel interactions in headwater catchments surprisingly little attention has been paid to such processes in lowland rivers in particular previous studies have not addressed the influence of hillslope contributions and have concentrated solely on in bank floods rather than more complex out of bank cases accordingly we combine field monitoring and numerical modeling to study hillslope floodplain and channel interactions for a lowland river piezometric precipitation and river stage data were used to parameterize and test a new two dimensional finite element model of saturated unsaturated flow applied to two vertically aligned cross sections through a lowland floodplain data for two major out of bank flood events were simulated which appeared to show the presence of a significant unsaturated zone extending up to 5 m below the surface the model simulated reasonably well the pressure head field that was recorded at a number of piezometers located internal to the computational domain on each transect and we conclude that floodplain hydrology is predominately a two dimensional lateral process three dimensional down reach flow effects would seem to become more significant at the beginning and end of each event the simulations also showed that the unsaturated zone remained close to saturation at all times and that it was not significant in terms of the floodplain hydrology examination of velocity vector patterns showed the formation of a strong groundwater ridge within the floodplain this led to the development of strong velocities directed toward hillslope areas as the inundation front approached the hillslope floodplain junction this suggests that surface water may move into hillslope areas adjoining the floodplain during major floods thus the extent of the hyporheic zone may be larger than previously thought

comparison of measured and estimated unsaturated hydraulic conductivities during snowmelt estimates of unsaturated flow often require an assessment of the relationship between unsaturated hydraulic conductivity ku and moisture content measured ku relationships for a well sorted sandy soil were obtained using the instantaneous profile method during snowmelt recharge these values are compared with estimates from three approaches the campbell equation a modified version of the campbell model that considers residual water and the rate of isotopic tracer displacement during infiltration the modified campbell model provided the best fit to the observed data although all three methods overpredicted ku the isotopic tracer method overestimated observed ku values by 2 6 4 5 times this may reflect the role of macropores upon hydraulic conductivities during infiltration since the tracer method is employed during recharge while the instantaneous profile method is generally used during drainage periods when macropores are nonconductive whereas ku estimates derived from empirical approaches such as the campbell model may be valid during conditions of drainage the isotopic tracer model appears to provide more realistic conductivity values during infiltration the latter method also provides a direct means of estimating the immobile fraction of total soil water

the generation and quality of streamflow on inactive uranium tailings near elliot lake ontario this study was undertaken to investigate the physical and chemical interactions between groundwater and surface water in an area of inactive uranium mill tailings near elliot lake ontario the study area had a shallow water table and was drained by a single channel streamflow chemistry and discharge and the hydraulic response of the groundwater system were monitored for several runoff events during the period of september 1981 through may 1982 the hydrographs measured for each event were separated into groundwater and surface water components using the mass balance technique with cl and 18o as conservative tracers the mechanisms of streamflow generation and their effect on runoff quality were evaluated on the basis of the hydrograph separations the observed groundwater response and the characteristics of the precipitation events the results indicate that groundwater constitutes a significant amount of the stormflow generated in the study area the magnitude of this contribution was dependent upon the intensity and duration of rainfall and on the initial depth to the water table the capillary fringe played an important role in the processes of streamflow generation both in causing a large water table rise which increased groundwater flow to the stream and in forming an expanding seepage face which enhanced overland flow during runoff events the stream contained high concentrations of several dissolved inorganic species the groundwater contribution was a major source of these constituents the findings of this study indicate that groundwater can be a major component of streamflow during runoff events in inactive tailings areas and as a result can have a major influence on runoff quality the groundwater contribution to streamflow represents an important pathway of contaminant migration to the biosphere which can be anticipated to persist for long periods of time

mixing of event and pre event water in a shallow entisol in sloping farmland based on isotopic and hydrometric measurements sw china

the late quaternary geology of the chalk river region ontario and quebec glacial ice covered the chalk river area through most of the wisconsin stage about 11 300 years ago an ice retreat was followed immediately by a short incursion of champlain sea waters which deposited at least 2 5 m of clay silt and sand a local readvance probably associated with the st narcisse event deposited till on the marine sediments following the final retreat of the ice from the area lacustrine and aeolian deposition occurred locally for a short time about 10 500 years ago the north bay drainage route opened greatly increasing the discharge of the ottawa river a faint terrace at a present elevation of 209 m probably formed at this time changes in the drainage routes of proglacial lakes and in the rate of ice retreat caused a general decrease in discharge rates and resulted in the formation of pronounced terraces now at 180 160 and 129 m and fainter terraces at 170 141 and 137 m by about 5000 years bp the north bay outlet closed and the river fell to approximately 111 m it

reading of the trigger records of sedimentary events a problem for future studies abstract sedimentary records of various three to four dimensional patterns of nature have recently attracted the special attention of many geologists the dramatic development of rhythmic sequence stratigraphy is a conspicuous recent instance the significance of event sedimentation in geohistory however has not been examined sufficiently the problem to how to read the records of triggers or thresholds of sedimentary events has been ignored the difficulty of solving this problem concerns the difference in patterns between natural sedimentary processes and their resulting sediments terminological confusion of event deposits is another cause which hinders our taking note of this problem a few examples of endeavours to discriminate the threshold of sedimentary events are shown by the analysis of two kinds of turbidites of the mid guatemala trench the investigation of slump derived turbidites of the suruga trough and the study of the seismoturbidites in lake biwa well focused investigations of features of trigger known sediments is the best strategy to find the criteria for discriminating the triggers or thresholds based on sedimentary records of various sedimentary events from this point of view more detailed studies of the santorini eruption induced homogenites the k t boundary impact induced tsunamiites together with the lake biwa seismic turbidites are very important further efforts should be made to find and investigate as many trigger identifiable sediments as possible

numerical modelling of tsunami propagation with implications for sedimentation in ancient epicontinental seas the lower jurassic laurasian seaway abstract tsunamis are frequent events in modern marine environments but evidence of their passing in subtidal ancient epicontinental sea deposits is elusive it has been suggested that this is due to mis identification or poor preservation potential herein a numerical modelling approach is used to show that tsunami propagation in one large ancient epicontinental sea was hindered by the damping effect of shallow bathymetries and reflection refraction and diffraction from emergent landmasses the imperial college ocean model icom is used for this study and is first validated against data from the sumatra andaman tsunami of december 2004 a palaeobathymetric dataset is then presented for the hettangian lower jurassic laurasian seaway with idealised tsunami sources situated on the continental shelf and within the adjacent oceanic basin results show that tsunamis forced from within ocean basins adjacent to the epicontinental sea are rapidly attenuated over the continental slope and fail to propagate great distances onto the shelf similarly the sedimentological effect of tsunamis forced from within the epicontinental sea is also restricted it is concluded that tsunami deposits in ancient epicontinental seas are most likely to occur in relative proximity to the source region and this must contribute to their scarcity in the geological record

introduction to special issue of canadian journal of earth sciences the trans hudson orogen transect of lithoprobe dedication dr john f lewry 1939 1999 see saskatchewan geological survey 1999 dedicated his career to investigations of the saskatchewan manitoba segment of the trans hudson orogen tho one of the principal paleoproterozoic orogens associated with the assembly of laurentia indeed one can make a strong case that lithoprobe s trans hudson orogen transect thot was designed to test the tectonic models proposed by john lewry he delineated the distinct tectonic provinces in the western part of the tho predicted the presence of an archean craton trapped within the tho and recognized and interpreted the significance of the pelican thrust between the juvenile paleoproterozoic volcanic arc complex of the western flin flon domain and the archean craton now called the sask craton the research published in lewry and stauffer 1990 and many of his ideas provided the framework for the design of the thot geophysical and geological studies john lewry was co leader of the thot until he passed away in 19

identifying the water source for subsurface flow with deuterium and oxygen 18 isotopes of soil water collected from tension lysimeters and cores the conventional identification of soil water with pre event water limits deep insights into the involvement of stationary and mobile soil water in subsurface hydrological processes in three tilled sloping field plots at a hilly area of southwestern china dominated by entisols soil water collected with a suction lysimeter was distinguished from the total soil water through an analysis of the stable isotopes deuterium and oxygen 18 differences in the depth profile of soil water before and after storm events were observed and used to examine how rainwater mixes with soil water and to identify the source contribution of different fractions of soil water in subsurface flow generation only water in the 0 10 cm soil layer was significantly affected by evaporation and infiltration water in the top 5 cm layer of the soil exhibited the lowest residence time because a storm can replace a substantial proportion of the pre event water soil water at the 10 20 cm depth showed the longest residence time as indicated by its high proportion of pre event water the isotopic signatures demonstrated that piston flow and preferential flow coexisted in this soil high antecedent soil water content and high rain intensity favor the formation of piston flow the water collected with the suction lysimeter represented the mobile fraction of the pre event water in the soil which effectively participates in the generation of subsurface flow newly infiltrated rainwater did not well mix with stationary pre event water in the soil the use of recent rainfall to represent mobile soil water may provide a practical solution for overcoming the negative effect of the spatial heterogeneity of the isotopic composition of soil water on hydrograph separation results bulk soil water and lysimeter water showed significant differences in isotopic composition under low soil water content or in the top soil layer stable isotopes in bulk and lysimeter soil water should be monitored synchronously to reveal the sources and pathways of soil water and their contributions to the generation of subsurface flow in the vadose zone c 2013 elsevier b v all rights reserved

the capillary fringe and its effect on water table response abstract shallow water tables are often observed to respond in a highly disproportionate manner to precipitation events that is the magnitude of the response is often much greater than would be predicted on the basis of the specific yield of the geologic material and the amount of rainfall physical arguments are presented to show that if the capillary fringe the zone of tension saturation extends to ground surface then the addition of a very small amount of water can result in an immediate and large rise in the water table the arguments are supported by a field experiment in which the addition of 0 3 cm of water caused the water table to rise 30 cm in 0 25 min thus demonstrating the large and highly transient influence of the capillary fringe on the position of the water table the evidence in this study as well as recent work of others suggests that the capillary fringe effect could have a major influence on the process of stream flow generation contaminant transport to surface waters and contaminant transport in hydrogeologic regimes having shallow water tables it is further shown that calculations of groundwater recharge and consumptive use based on water table response and an assumed specific yield could be substantially in error

evidence from crater ages for periodic impacts on the earth recent evidence has indicated that the impact of a comet or asteroid may have been responsible for mass extinction at the ends of both the cretaceous1 and the eocene2 4 quantitative analysis by raup and sepkoski5 showed that mass extinctions occur with a 26 myr period similar to the period seen in qualitative pelagic records by fischer and arthur6 to account for the possibility of periodic comet showers davis et al 7 proposed that such showers could be triggered by an unseen solar companion star as it passes through perihelion on a moderately eccentric orbit to test a prediction implicit in this model we examined records of large impact craters on the earth we report here that most of the craters occur in a 28 4 myr cycle within measurement errors this period and its phase are the same as those found in the fossil mass extinctions the probability that such agreement is accidental is 1 in 103

lateral moisture flow beneath a sandy hillslope without an apparent impeding layer part of a small drainage basin on the sevilleta national wildlife refuge about 25 km north of socorro nm was intensively instrumented with soil monitoring equipment to estimate natural ground water recharge soil moisture data were analysed with special attention to characterizing the influence of topography on the direction of vadose water flow paths in fine to medium aeolian sand moisture content data were obtained by the neutron scattering technique and hydraulic head data were obtained using tensiometers in addition tracer experiments were conducted on a sandy hillslope to delineate the flow paths of vadose water the results indicate that there is a strong lateral component to unsaturated flow on a hillslope even in the absence of apparent sublayers of much lower permeability darcian calculations estimate the long term steady deep flux beneath a concave location to be about 4 per cent of an assumed mean annual precipitation of 20 cm the deep soil water flux downward varied by several orders of magnitude during the 17 month period of record

water table fluctuations within the floodplain of the river severn england abstract in contrast to extensive research on hydrological processes operating in headwater basins there has been relatively little attention paid to the hydrological processes that occur on the floodplains of lowland rivers this dearth of information is all the more surprising given current interest in the use of floodplains as buffer zones between farmland and the riverine environment in the previous paper water resour res 36 2000 2517 bates et al reported preliminary results from a field site on the floodplain of the river severn in shropshire uk a large lowland river by british standards piezometric data suggested that during out of bank conditions a reverse groundwater ridge develops in the floodplain subsurface and results in strong groundwater flux velocities directed towards the base of hillslopes adjoining the floodplain bates et al showed that the impact of such ridges was to switch off hillslope inputs to the riparian zone they hypothesised that this occurred when surface inundation approached the back of the floodplain in this paper we provide a more detailed analysis of the events considered by bates et al and extend the analysis to the more common in bank flood condition in total five events are considered two out of bank and three in bank these were chosen to represent a wide range of event magnitudes antecedent conditions and local patterns of rainfall and runoff the analysis demonstrates that the reverse groundwater ridging process identified by bates et al also occurs during in bank events hillslope inputs to the floodplain are also switched off in these events if the flood stage is high in smaller floods water continues to move from slope to floodplain although coupling between slope and channel is only re established later in the recession we conclude that contrary to the conclusions of bates et al this process switching is not necessarily dependent on surface inundation approaching the back of the floodplain whilst the paper broadly confirms the operation of the simple reverse groundwater ridging process described by bates et al it shows that antecedent conditions local rainfall and runoff and flood stage all act to complicate this basic pattern lastly we consider the implications for catchment water quality of the newly identified processes

groundwater surface water interactions in headwater forested wetlands of the canadian shield abstract groundwater and surface water interaction in two conifer swamps located in headwater catchments with contrasting till depth typical of the southern canadian shield were studied from june 1990 to august 1992 both swamps had little influence on the regulation or attenuation of seasonal runoff response in the catchment the two valley bottom swamps were connected to local aquifers but the upland wetland connection was continuous in the catchment with deeper till and ephemeral in the catchment with thin till rock ridges groundwater movement through the wetlands was restricted mainly to the surface peat layer in both wetlands because a large portion of inputs from shallow soil layers and stream inflows enter near the peat surface however differences in upland wetland connections resulted in contrasting hydrologic regimes in the two swamps during seasons with larger inputs both swamps were hydrologically connected to uplands and had a similar hydrology characterized by a high water table rapid storm response and predominance of saturated overland flow in summer upland inputs were absent in the catchment with thin till rock ridges resulting in cessation of baseflow and a lower water table that varied in response to variations in rainfall continuous upland inputs throughout the summer in the catchment with deeper tills 1 3 m sustained baseflow and kept the water table near the peat surface this study demonstrates the control of morphology and shallow subsurface geology on the hydrology of valley bottom swamps influenced by local aquifers

snowmelt infiltration and storage within a karstic environment vers chez le brandt switzerland summary even though karstic aquifers are important freshwater resources and frequently occur in mountainous areas recharge processes related to snowmelt have received little attention thus far given the context of climate change where alterations to seasonal snow patterns are anticipated and the often strong coupling between recharge and discharge in karst aquifers this research area is of great importance therefore we investigated how snowmelt water transits through the vadose and phreatic zone of a karst aquifer this was accomplished by evaluating the relationships between meteorological data soil water content vadose zone flow in a cave 53 m below ground and aquifer discharge time series data indicate that the quantity and duration of meltwater input at the soil surface influences flow and storage within the soil and epikarst prolonged periods of snowmelt promote perched storage in surficial soils and encourage surficial lateral flow to preferential flow paths thus in karstic watersheds overlain by crystalline loess a typical pedologic and lithologic pairing in central europe and parts of north america soils can serve as the dominant mechanism impeding infiltration and promoting shallow lateral flow further hydrograph analysis of vadose zone flow and aquifer discharge suggests that storage associated with shallow soils is the dominant source of discharge at time scales of up to several weeks after melt events while phreatic storage becomes import during prolonged periods without input soils can moderate karst aquifer dynamics and play a more governing role on karst aquifer storage and discharge than previously credited overall this signifies that a fundamental understanding of soil structure and distribution is critical when assessing recharge to karstic aquifers particularly in cold regions

migration of contaminants in groundwater at a landfill a case study 4 a natural gradient dispersion test abstract a natural gradient tracer test using a chloride solution with an initial injection volume of 0 7 m 3 was performed in the sandy aquifer at the borden site the solution was injected into five well points set 1 m below the water table in an uncontaminated zone situated above the contaminant plume at a location 450 m downflow from the landfill under conditions of natural groundwater flow the tracer slug was monitored for a period of 4 months by withdrawing small volume samples from points in a three dimensional array of bundle type multilevel samplers measurements of hydraulic head were obtained from a network of miniature piezometers soon after injection the tracer slug gradually split into two halves one half moving horizontally at an average velocity of 2 9 10 6 ms 1 and the other horizontally at 8 2 10 7 ms 1 although the split has been attributed to local lateral heterogeneity the nature of the heterogeneity and its influence on the hydraulic head distribution were not clearly distinguishable in the field data obtained before during or after the test the chloride patterns for each of the two halves of the tracer slug evolved into gaussian forms although the patterns demonstrated some irregularity at early time the relatively smooth gaussian forms were unexpected because the aquifer has numerous small scale heterogeneities observed in vertical cores obtained from the tracer zone and because the glaciofluvial origin of the aquifer suggests that heterogeneities are not laterally continuous simulated chloride distributions from a three dimensional analytical solution to the advection dispersion equation were fitted to the field data to obtain best fit estimates of the values of longitudinal transverse horizontal and transverse vertical dispersivity at various travel distances for each of the two halves of the tracer zone this is the first known field test that has permitted the estimation of three principal dispersion coefficients in layered media the longitudinal dispersivity was found to increase from 0 01 m at a distance of 0 75 m from the source to 0 08 m at 11 0 m the transverse horizontal dispersivity increased also to a value of 0 03 m at 11 0 m transverse vertical dispersion was very weak and was accounted for by molecular diffusion the relative lack of vertical dispersion is consistent with the shape of the plume of leachate contamination from the landfill it was concluded that the observed increase in dispersivity along the path of migration is likely caused by heterogeneities information on the dispersion controlling heterogeneities is not yet available as practical field methodologies for their identification and description have not yet been developed until such information is incorporated into mass transport models a realistic solution of the dispersion problem in heterogeneous media will remain elusive

reconstruction of the holocene seismotectonic activity of the southern andes from seismites recorded in lago icalma chile 39 s abstract south central chile is one of the most geodynamically active areas in the world characterized by frequent volcanic eruptions and numerous earthquakes which are both recorded in lake sediments in lago icalma 39 s long piston and short gravity coring as well as 3 5 khz high resolution seismic profiling have been carried out in order to study the holocene sedimentary infill of the lake with a special focus on earthquake triggered deposits macroscopic description of sediment cores and detailed grain size analyses allow us to identify four types of seismically induced deposits or seismites slump deposits chaotic deposits turbidites s s and homogenites homogenites are characterized by the occurrence of three distinct units on grain size profiles i e a coarse base a thick homogeneous unit topped by a thin layer of very fine sediment and by the typical distribution of the grain size parameters in a skewness sorting diagram while turbidites s s are characterized by a continuous fining upward trend radiocarbon 210pb dating and tephrochronology allow us to demonstrate that the regional seismotectonic activity was probably very high between 2200 and 3000 cal years bp as well as between 7000 and 8000 cal years bp and that none of the historically documented earthquakes has triggered a seismite in lago icalma the most recent seismite recognized in the sediments of lago icalma is a slump deposit dated at 1100 100 ad i e older than the period covered by historical records the remarkable record of seismites between 2200 and 3000 cal years bp is probably influenced by a major eruption of sollipulli volcano at 3000 cal years bp which has rejuvenated the stock of terrigenous particles available for erosion by depositing a thick layer of pumices all over the watershed of lago icalma and by clearing the vegetation covering the volcanic ash soils this paper demonstrates that the record of seismically triggered deposits in lake sediments is not only controlled by the intensity of the triggering earthquake and the occurrence of unstable sediment along the lake slopes but also by the presence of particles available for erosion remobilisation in the watershed

numerical simulation of infiltration and solute transport in an s shaped model basin by a boundary fitted grid system abstract the boundary fitted grid method which transforms a complicated computational domain into a rectangular domain is applied for the moisture and solute transport problems in the unsaturated soil layer of an s shaped model hillslope in the transformed domain the fundamental equations of moisture and solute transport i e the richards equation and the fickian equation can be easily discretized into the finite difference form for three types of rainfall pattern a unit rainfall two unit successive rainfalls and two unit ranfalls with a lag between them hydrographs of total pre event and event water and event water discharges contour lines of soil moisture pressure and total hydraulic head distributions and flow velocity vectors are compared for a relatively thick soil layer or for a relatively light rainfall the capillary fringe effect plays an important role whereas for a relatively thin soil layer or for a relatively heavy rainfall overland flow from a variable source area is superimposed on the capillary fringe type runoff

towards establishing criteria for identifying trigger mechanisms for soft sediment deformation a case study of late pleistocene lacustrine sands and clays onikobe and nakayamadaira basins northeastern japan five main deformation units discrete sheets of deformed sediments that lie between a significant thickness of undeformed sediment were selected for study within late pleistocene lacustrine sands and clays in the onikobe and nakayamadaira basins northeastern japan the deformed units show evidence of deformation by a variety of mechanisms including fluidization liquefaction brittle failure and cohesive flow driving forces are thought to be primarily reverse density gradient systems but also include gravitational body force shear stress and unequal loading the main trigger mechanisms are firstly earthquakes secondly overloading from volcanic sands and thirdly to a lesser extent subaqueous currents consideration is given to criteria that allow the trigger mechanism to be identified this study shows that the following criteria can be used to identify a seismic triggering agent i setting ii the extent of the deformation units iii absence of evidence relating to other potential trigger mechanisms and iv evidence relating to other potential trigger mechanisms is present but can be seen elsewhere in the stratigraphic section associated with undeformed sediment conversely the following criteria while they are important in interpreting the driving force and deformation mechanism have no relevance to the trigger mechanism i sediment composition ii deformation structures being restricted to a single stratigraphic interval 1 m thick not necessarily correlatable over large areas and iii similarity to structures in the literature

improved dissolution and chemical separation methods for lu hf garnet chronometry 1 garnet based lu hf geochronology using conventional hf hno3 dissolution methods may be compromised by full or partial digestion of hf rich zircon inclusions this study integrates two complimentary methods to substantially reduce zircon digestion while assuring complete digestion of garnet and sample spike equilibration handpicked garnet fractions are heat treated to 1000 c in an evacuated silica glass ampoule to anneal zircon inclusions and then dissolved with 12 m hcl at 210 c and cold 28 m hf analyses of heat treated garnet and their high temperature breakdown products orthopyroxene spinel quartz from gore mountain new york demonstrate the method is capable of complete dissolution of garnet and routinely achieving sample spike equilibration independent analyses of annealed and unannealed zircons dissolved by hcl cold hf demonstrate the benefit of heat treatment prior to dissolution analyses of zircon rich garnets from peletic paragneisses of labrador canada show the potential of this method by returning lu hf ratios commensurate with the degree of heat treatment finally a complementary chemical separation method for lu and hf is presented that supports analysis of garnet by mc icp ms

proximal impact deposits at the cretaceous tertiary boundary in the gulf of mexico a restudy of dsdp leg 77 sites 536 and 540 restudy of deep sea drilling project sites 536 and 540 in the southeast gulf of mexico gives evidence for a giant wave at cretaceous tertiary boundary time five units are recognized 1 cenomanian limestone underlies a hiatus in which the five highest cretaceous stages are missing possibly because of catastrophic k t erosion 2 pebbly mudstone 45 m thick represents a submarine landslide possibly of k t age 3 current bedded sandstone more than 2 5 m thick contains anomalous iridium tektite glass and shocked quartz it is interpreted as ejecta from a nearby impact crater reworked on the deep sea floor by the resulting tsunami 4 a 50 cm interval of calcareous mudstone containing small cretaceous planktic foraminifera and the ir peak is interpreted as the silt size fraction of the cretaceous material suspended by the impact generated wave 5 calcareous mudstone with basal tertiary forams and the uppermost tail of the ir anomaly overlies the disturbed interval dating the impact and wave event as k t boundary age like beloc in haiti and mimbral in mexico sites 536 and 540 are consistent with a large k t age impact at the nearby chicxulub crater

episodic sedimentation how normal is average how rare is rare does it matter where repeated sharp changes of sedimentation are inescapable periodic cycles are commonly invoked to preserve uniform orderly variations from some supposed norm the sedimentary record rarely reflects such uniformity however as sedimentologists have gradually realized magnitude versus frequency of processes has received little attention in sedimentology recurrence interval recovery time and preservation potential are critical factors for evaluating their significance for the sedimentary record large magnitude processes which represent positive deviations from the norm and are rare on the human time scale must be significant over geologic time everyday processes may have obliterated much of the evidence the sedimentological importance of rare events is difficult to assess because the record of such events may be very subtle this is especially true if a deposit has been thoroughly bioturbated or if the record of an event is simply an erosional surface it has now become possible to evaluate quantitatively ancient episodic sedimentation using modern process rates as well as refined biostratigraphic and isotopic dating i predict that such evaluation will necessitate revision of our favorite depositional models which have become so important for exploration as well as for research modified journal abstract

sedimentary features of seismites seismo turbidites and tsunamiites an introduction abstract catastrophic events such as deposits from sediment flows generated by seismic events or major tempests have not been intensively studied sedimentological procedures for deducing the relationships of seismic foci intensity period and amplitude of the seismic waves have been initiated only recently this special volume arose from a session entitled sedimentary features of seismites seismo turbidites and tsumaniites held at the 15th international sedimentological congress in alicante spain in april 1998 the papers in this volume cover a somewhat broader range of subjects our goal is to stimulate further research on the sedimentary features of seismites seismoturbidites and tsunamiites

hydrologic response of catchments to precipitation quantification of mechanical carriers and origins of water 1 precipitation induced overland and groundwater flow and mixing processes are quantified to analyze the temporal event and pre event water and spatial groundwater discharge and overland runoff origins of water entering a stream using a distributed parameter control volume finite element simulator that can simultaneously solve the fully coupled partial differential equations describing 2 d manning and 3 d darcian flow and advective dispersive transport mechanical flow driven by hydraulic potential and tracer based hydrograph separation driven by dispersive mixing as well as mechanical flow are simulated in response to precipitation events in two cross sections oriented parallel and perpendicular to a stream the results indicate that as precipitation becomes more intense the subsurface mechanical flow contributions tend to become less significant relative to the total pre event stream discharge hydrodynamic mixing can play an important role in enhancing pre event tracer signals in the stream this implies that temporally tagged chemical signals introduced into surface subsurface flow systems from precipitation may not be strong enough to detect the changes in the subsurface flow system it is concluded that diffusive dispersive mixing capillary fringe groundwater ridging and macropore flow can influence the temporal sources of water in the stream but any sole mechanism may not fully explain the strong pre event water discharge further investigations of the influence of heterogeneity residence time geomorphology and root zone processes are required to confirm the conclusions of this study

hydrology of subarctic canadian shield soil filled valleys the canadian shield landscape includes bedrock uplands and valleys infilled with soil a site near yellowknife in subarctic canada was studied to elucidate the hydrological behaviour of soil filled valleys a suite of hydrological processes was found to be important in the studied valley including snowmelt and rainfall ground frost development evaporation infiltration lateral inflow from adjacent uplands and surface and subsurface flows valley storage requirements during snowmelt are met by local meltwater infiltration but lateral inflows in the summer are needed to satisfy the storage before runoff can be generated from the valley the valleys perform three functions of collecting vertical and lateral water inputs retaining and losing the water held in storage and transferring water down the valley and generating local outflow unlike channel flows in humid areas runoff from the upper valley has to meet the storage demands of the lower valley segments often causing seepage loss along flow paths to render the flows intermittent a fill and spill runoff system is proposed in which the valley physiography results in a series of segments with varying storage conditions as water is supplied to the valley each segment has to be filled until its storage threshold for runoff is exceeded then subsurface or surface flows will be generated but these flows may be arrested to furnish water to satisfy the storage requirements of the segments downstream such a flow system applies also to other valleys in the shield environment

ostracoda crustacea as indicators of subaqueous mass movements an example from the large brackish lake tangra yumco on the southern tibetan plateau china abstract a conceptual model of subaquaeous mass movements and ostracod distribution in lacustrine sediment event layers was tested integrated methods geophysical sedimentological and microfossil analyses were performed on a short sediment core retrieved from 220 m water depth in the large brackish lake tangra yumco on the southern tibetan plateau central asia the event layers of the core and their underlying and overlying sediments were investigated four major event layers composed of sandy silt with graded bedding are interpreted as turbidites the fifth layer consisting of fine sand and silt and without graded bedding is characterized as a debrite the ostracods small bivalved aquatic crustaceans identified are leucocytherella sinensis huang 1982 leucocythere dorsotuberosa huang 1982 limnocythere inopinata baird 1843 and fabaeformiscandona gyirongensis huang 1982 ostracod evidence is a good proxy for the evaluation of massive sediment event layers formed by subaqueous mass movements four assumptions of a conceptual model were confirmed i fine grained sediments of event layers turbidite deposits contain very low numbers of ostracods compared to the underlying and overlying sediments ii ostracods are sorted according to size and display high abundance and high proportion of adult valves of leucocytherella sinensis at the base of event layers iii a relatively low number of carapaces is present within the event layers and iv the recolonization of newly event generated habitats by pioneer assemblages transforming into pre event association gradually

ca isotope cycling in a forested ecosystem reports of large ca isotope fractionations between trees and soils prompted this study of a boreal forest ecosystem near la ronge saskatchewan to improve understanding of this phenomenon the results on five tree species black spruce trembling aspen white spruce jack pine balsam poplar confirm that nutrient ca uptake by plants favors the light isotopes thus driving residual ca in plant available soil pools towards enrichment in the heavy isotopes substantial within tree fraction occurs in tissues formed along the transpiration stream with low 44ca values in fine roots 2 mm intermediate values in stemwood and high values in foliage separation factors between different plant tissues are similar between species but the initial fractionation step in the tips of the fine roots is species specific and or sensitive to the local soil environment soil water 44ca values appear to increase with depth to at least 35 cm below the top of the forest floor which is close to the deepest level of fine roots the heavy plant fractionated signature of ca in the finely rooted upper soils filters downward where it is retained on ion exchange sites leached into groundwater and discharged into surface waters the relationship between ca uptake by tree fine roots and the pattern of 44ca enrichment with soil depth was modeled for two ca pools the forest floor litter and the underlying upper b mineral soil six study plots were investigated along two hillside toposequences trending upwards from a first order stream we used allometric equations describing the ca distribution in boreal tree species to calculate weighted average 44ca values for the stands in each plot and estimate ca uptake rates the 44ca value of precipitation was measured and soil weathering signatures deduced by acid leaching of lower b mineral soils steady state equations were used to derive a set of model ca fluxes and fractionation factors for each plot the model reproduces the increase in 44ca with depth found in forest floor and upper b soil waters transient model runs show that the forest ca cycle is sensitive to changes in plant ca uptake rate such as would occur during ontogeny or disturbance accordingly secular records of 44ca in tree ring cellulose have the potential to monitor changes in the forest ca cycle through time thus providing a new tool for evaluating natural and anthropogenic impacts on forest health another model run shows that by changing the size of the isotope fractionation factor and adjusting for differences in forest productivity that the range in ca isotope fractionation in forested ecosystems reported in the literature thus far is reproduced as a quantitative tool the ca cycling model produces a reasonable set of relative ca fluxes for the la ronge site consistent with environment canada s measurements for wet deposition in the region and simulated ca release from soil mineral weathering using the profile model but the sensitivity of the model is limited by the small range of fractionation observed in this boreal shield setting of 1 which limits accuracy if the model were applied to a site with a greater range in 44ca values among the principal ca fluxes it is capable of producing robust and reliable estimations of ca fluxes that are otherwise difficult to measure in forested ecosystems

study of tracer movement through unsaturated sand abstract a column of 100 cm length and 15 4 cm diameter was filled with sand a solute displacement experiment using tritium as a tracer was conducted under saturated water flow conditions analysis of the observed effluent concentration resulted in an estimated dispersivity of 0 094 cm solute displacement experiments under unsaturated water flow conditions were conducted by leaching the column intermittently on a daily basis with constant amounts of water as soon as the amount drained from the column was equal to the daily input tritium was added to the infiltrating water for some period three such experiments were conducted with different amounts of water infiltrated daily these amounts were small enough for the water flow to remain unsaturated the parameters of the hydrodynamic dispersion equation were fitted to the observed effluent concentrations very large dispersion coefficients were obtained with a dispersivity of about 7 3 cm a possible explanation of this phenomenon is the presence of immobile water pockets during unsaturated flow for all experiments it was found that about 36 of the water in the unsaturated column could be considered as immobile the exchange of solute between the mobile and immobile phases explains very well the large dispersion observed in the experiments conducted under unsaturated conditions

seismoturbidites a new group of resedimented deposits abstract turbidite beds of exceptionally large volume and areal extent occur in both modern and ancient deep water basins these beds which may reach individual volumes in excess of 100 km3 are apparently the product of catastrophic gravity flows triggered by earthquakes along the margins of highly mobile basins most commonly elongate flysch troughs turbidite beds produced by these catastrophic events are generally characterized by very distinctive geometry internal structures and composition and are termed herein seismoturbidites characteristically these sediments lack time persistent features of deep sea fans such as channels and lobes seismoturbidites may occur as scattered intercalations diluted within otherwise normal turbidite sequences thus forming generally excellent markers for basin wide correlations or as closely spaced repetitive units comprising the bulk of the sedimentary fill of certain flysch basins in both cases they may offer a tremendously useful tool for a better understanding of the distribution of paleoseismic zones in time and space

deep sea drilling project site 612 bolide event new evidence of a late eocene impact wave deposit and a possible impact site u s east coast a remarkable 60 m thick upward fining polymictic marine boulder bed is distributed over 15 000 km sup 2 beneath chesapeake bay and the surrounding middle atlantic coastal plain and inner continental shelf the wide varieties of clast lithologies and microfossil assemblages were derived from at least seven known cretaceous paleocene and eocene stratigraphic units the supporting pebbly matrix contains variably mixed assemblages of microfossils from the same seven stratigraphic units along with trace quantities of impact ejecta tektite glass and shocked quartz the youngest microfossils in the boulder bed are of early late eocene age on the basis of its unusual characteristics and its stratigraphic equivalence to a layer of impact ejecta at deep sea drilling project dsdp site 612 new jersey continental slope the authors postulate that this boulder bed was formed by a powerful bolide generated wave train that scoured the ancient inner shelf and coastal plain of southeastern virginia the most promising candidate for the bolide impact site identified on seismic reflection profiles is 40 km north northwest of dsdp site 612 on the new jersey outer continental shelf

episodic paleoproterozoic crustal growth preserved in the aillik domain makkovik province labrador abstract the convergent margin of southeastern laurentia consists of reworked continental crust as well as accretion of continental ribbons and juvenile arc terranes forming part of the great proterozoic accretionary orogen the makkovik orogen in labrador preserves evidence of the timing duration and complexities of these accretionary events during the interval 1 88 1 78 ma new regional bedrock geological mapping combined with new u pb zircon shrimp ages constrain the paleoproterozoic felsic magmatism in the aillik group of the makkovik orogen nine samples from the aillik group yield magmatic 207pb 206pb ages between 1883 7 ma and 1858 3 ma the ages extend the previously documented ages of felsic volcanism providing evidence for periodic volcanism spanning 35 m y with the most prolific volcanic activity occurring ca 1860 ma combined with previous studies the aillik group is now constrained between 1883 7 and 1848 2 7 ma development of a pervasive planar fabric associated with the northwestward thrusting of the aillik group d3 occurred after 1848 ma lithotectonic evolution in the makkovik province comprised significant crustal reworking magmatism and minor preserved juvenile crustal growth between ca 1883 and 1848 ma the revised model for formation of the aillik group proposed herein suggests that the aillik group formed in a continental back arc setting these new ages further refine the timing of the accretionary events as well as characterizing the age of the crustal root of the arc which could be a juvenile substrate neoarchean paleoproterozoic or reworked archean crust possibly the 2 3 2 6 ma mistinibi raude crust of the southeast churchill province

correlation chart of the proterozoic assembly of the northeastern canadian greenland shield chart 1 correlation chart of the proterozoic assembly of the northeastern canadian greenland shield including a location map and reference list

simulation of water flow on irrigation bay scale with mike she this study focuses on water flow of a 9 ha experimental irrigation site in a shallow water table area in the tragowel plains australia with the aim of quantifying the processes affecting surface drainage and groundwater levels the irrigation site was intensively monitored to provide the required input and calibration data for modelling the physical processes simulation of flow processes including infiltration capillary rise evapotranspiration overland flow groundwater exfiltration and groundwater flow into the drain was performed using the physically based distributed model mike she the model was calibrated against the observed piezometric levels drain flow and soil moisture data collected over a 19 month period that represented different field conditions under seasonal changes model simulations were generally consistent with the observed data however the results highlighted inadequacies of the model particularly in representing variations in rapid flow through macropores that occur due to the cracking and swelling properties of the soil despite this deficiency the modelling study allowed quantification of the effective flow processes and provided an insight into their implications in determining the quality i e salinity and quantity of drain flow and groundwater levels

effects of vadose zone on groundwater table fluctuations in unconfined aquifers summary above a shallow unconfined aquifer a considerable amount of water is stored in the vadose zone through water exchange with the underlying unconfined aquifer the vadose zone affects the groundwater table dynamics and overall behavior of the aquifer in this paper we examine tide induced groundwater table fluctuations in unconfined aquifers influenced by vadose zone of finite thickness under the condition of small aquifer thickness d compared with the groundwater wavelength l i e 2 d l 2 1 and small boundary oscillation amplitude a i e e a d 1 where 2 and e are two parameters an approximate analytical solution was derived to quantify systematically the vadose zone effects with a particular consideration of capping by the ground surface i e the upper boundary of the vadose zone depending on the extent to which the capillary rise is truncated by the ground surface the vadose zone enhances the groundwater table fluctuations in an unconfined aquifer however the mean groundwater table height and exchange between surface water and groundwater are reduced due to the presence of the vadose zone these effects are intensified with increased capillary rise but weakened as the vadose zone thickens this study provides a criterion for assessing the importance of vadose zone in modulating the response of unconfined aquifers to low frequency forcing oscillations such as tides

towards the geological past abstract awareness of the necessity of environmental protection and nature conservation increases rapidly in both industrial and developing countries measures taken by authorities do however not always contribute to a natural development of the environments that they want to protect this is due partly to insufficient insight into the complexity of the natural processes playing a role in the various modern environments partly to unawareness of natural changes that occur in the course of time due to lateral and consequently also vertical facies changes a greater involvement of earth scientists who are aware of the time factor might contribute to more efficient and cost effective measures

migration of contaminants in groundwater at a landfill a case study 1 groundwater flow and plume delineation abstract a landfill derived contaminant plume with a maximum width of 600 m a length of 700 m and a maximum depth of 20 m in an unconfined sand aquifer was delineated by means of a monitoring network that includes standpipe piezometers multilevel point samplers and bundle piezometers the extent of detectable contamination caused by the landfill which began operation in 1940 and which became inactive in 1976 was determined from the distributions of chloride sulfate and electrical conductance in the sand aquifer all of which have levels in the leachate that are greatly above those in uncontaminated groundwater the maximum temperature of groundwater in the zone of contamination beneath the landfill is 12 c which is 4 5 c above background the thermal plume in the aquifer extends 150 m downgradient from the centre of the landfill a slight transient water table mound exists beneath the landfill in the late spring and summer in response to snowmelt and heavy rainfall beneath the landfill the zone of leachate contamination extends to the bottom of the aquifer apparently because of transient downward components of hydraulic gradient caused by the water table mound and possibly because of the higher density and lower viscosity of the contaminated water values of hydraulic conductivity which show variations due to local heterogeneity were obtained from slug tests of piezometers from pumping tests and from laboratory tests because of the inherent uncertainty in the aquifer parameter values the 38 yr frontal position of the plume calculated using the darcy equation with the assumption of plug flow can differ from the observed frontal position by many hundreds of metres although the use of mean parameter values produces a close agreement the width of the plume is large relative to the width of the landfill and can be accounted for primarily by variable periods of lateral east and westward flow caused by changes in water table configuration due to the variable nature of recharge northward from the landfill the vertical thickness of the plume decreases and the top of the plume is farther below the water table the thickness of the zone of uncontaminated groundwater above the plume increases northward as the area of recharge of uncontaminated water downflow from the landfill increases because dispersion in the vertical direction is weak there is very little mixing between the overlying zone of recharge water and the contaminant plume concentration profiles are irregular beneath and near the landfill and become smooth downgradient where the maximum concentrations are much less than those beneath landfill these features are attributed to a strong influence of longitudinal dispersion the plume passes beneath a small shallow stream near the landfill without significant influence on the stream

tracking water pathways in steep hillslopes by δ18o depth profiles of soil water assessing temporal variations in soil water flow is important especially at the hillslope scale to identify mechanisms of runoff and flood generation and pathways for nutrients and pollutants in soils while surface processes are well considered and parameterized the assessment of subsurface processes at the hillslope scale is still challenging since measurement of hydrological pathways is connected to high efforts in time money and personnel work the latter might not even be possible in alpine environments with harsh winter processes soil water stable isotope profiles may offer a time integrating fingerprint of subsurface water pathways in this study we investigated the suitability of soil water stable isotope d18o depth profiles to identify water flow paths along two transects of steep subalpine hillslopes in the swiss alps we applied a one dimensional advection dispersion model using d18o values of precipitation ranging from 24 7 to 2 9 as input data to simulate the d18o profiles of soil water the variability of d18o values with depth within each soil profile and a comparison of the simulated and measured d18o profiles were used to infer information about subsurface hydrological pathways the temporal pattern of d18o in precipitation was found in several profiles ranging from 14 5 to 4 0 this suggests that vertical percolation plays an important role even at slope angles of up to 46 lateral subsurface flow and or mixing of soil water at lower slope angles might occur in deeper soil layers and at sites near a small stream the difference between several observed and simulated d18o profiles revealed spatially highly variable infiltration patterns during the snowmelt periods the d18o value of snow 17 7 1 9 was absent in several measured d18o profiles but present in the respective simulated d18o profiles this indicated overland flow and or preferential flow through the soil profile during the melt period the applied methods proved to be a fast and promising tool to obtain time integrated information on soil water flow paths at the hillslope scale in steep subalpine slopes

recharge processes during snowmelt an isotopic and hydrometric investigation results from hydrometric and isotopic investigations of unsaturated flow during snowmelt are presented for a hillslope underlain by well sorted sands passage of melt and rainwater through the vadose zone was detected from temporal changes in soil water 2h concentrations obtained from sequential soil cores bypassing flow was indicated during the initial snowmelt phase but was confined to the near surface zone recharge below this zone was via translatory flow as meltwater inputs displaced premelt soil water estimates of premelt water fluxes indicate that up to 19 per cent of the premelt soil water may have been immobile average water particle velocities during snowmelt ranged from 6 2 10 7 to 1 1 10 6 ms 1 suggesting that direct groundwater recharge by meltwater during snowmelt was confined to areas where the premelt water table was within 1 m of the ground surface soil water 2h signatures showed a rapid response to isotopically heavy rain on snow inputs late in the melt in addition spatial variations in soil moisture content at a given depth induced a pronounced lateral component to the predominantly vertical transport of water both factors may complicate isotopic profiles in the vadose zone and should be considered when employing environmental isotopes to infer recharge processes during snowmelt

testing the groundwater ridging hypothesis of streamflow generation during snowmelt in a forested catchment hydrometric and isotopic techniques were used to test the groundwater ridging hypothesis of stream flow generation during snowmelt in a forested catchment on the canadian shield the catchment contains a central wetland that drains to an ephemeral channel hydrograph separation using 2h as a tracer indicated that approximately 60 of total stream flow during snowmelt was supplied by pre event water this was supported by hydrometric results however contrary to the groundwater ridging hypothesis the response of water table levels in near stream areas to initial melt inputs failed to promote a rapid flux of ground water to the wetland and stream all stream flow originated as saturation overland flow from the wetland and groundwater flow during much of the melt was directed down the catchment s main axis and back under hillslopes surrounding the wetland and channel although the hydrograph separation indicated pronounced short term variations in pre event discharge from the catchment groundwater fluxes to the wetland remained relatively invariant following initiation of surface saturation streamflow fluctuations appear to have been generated by displacement of water held in surface storage induced by melt and rainwater inputs to the wetland this stored water had an isotopic signature intermediate between that of event and pre event water suggested oscillations in pre event runoff were an artifact of the mixing model approach to hydrograph separation rather than the result of rapid changes in groundwater fluxes to the wetland

pliocene mass failure deposits mistaken as submarine tsunami backwash sediments an example from hornitos northern chile abstract in this study we question the former interpretation of a shallow marine backwash tsunami origin of a conspicuous pliocene coarse clastic unit at hornitos northern chile and instead argue for a debris flow origin for this unit we exclude a relation to a tsunami in general and to the eltanin impact in particular the observed deposit at hornitos was not generated either directly impact triggered tsunami or indirectly submarine mass flow caused by seismic shaking by an impact re calculation of the alleged impact tsunami including consideration of the van dorn effect shows that an impact in the southern ocean did not cause a significant tsunami at hornitos impact related seismic shaking was not able to trigger slides several thousands of kilometers away because the eltanin event was a deep sea impact that did not create a crater additionally the biostratigraphic age of 5 1 2 8 ma of the associated la portada formation is not concurrent with the newly established age of 2 511 0 07 ma for the eltanin impact instead we argue for an origin of the conspicuous unit at hornitos as a debris flow deposit caused by an earthquake in the andean subduction zone in northern chile our re interpretation considers the local synsedimentary tectonic background a comparison to recent submarine tsunami sediments and recent examples of mass wasting deposits along the chilean margin the increased uplift during the pliocene caused oversteepening of the coastal scarp and entailed a contemporaneous higher frequency of seismic events that triggered slope failures and cliff collapses the coarse clastic unit at hornitos represents an extraordinary potentially tsunami generating mass wasting event that is intercalated with mass wasting deposits on a smaller scale

geochronology and geochemistry of the enderbite series in the lapland granulite belt generation tectonic setting and correlation of the belt1nordsim publication no 322 the lapland granulite belt of the northeastern fennoscandian shield is dominated by blastomylonitic migmatitic metagreywackes and a deformed structurally conformable norite enderbite series the b

tektite bearing deep water clastic unit at the cretaceous tertiary boundary in northeastern mexico the hypothesis of cretaceous tertiary k t boundary impact on yucatan mexico predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves an outcrop along the arroyo el mimbral in northeastern mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic marl sequence deposited at more than 400 m water depth the marls were found to be unsuitable for determining magnetostratigraphy but foraminiferal biostratigraphy places the clastic unit precisely at the k t boundary we interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact the elastic unit comprises three main subunits 1 the basal spherule bed contains glass in the form of tektites and microtektites glass spherules replaced by chlorite smectite and calcite and quartz grains showing probable shock features this bed is interpreted as a channelized deposit of proximal ejects 2 a set of lenticular massive graded laminated beds contains intraclasts and abundant plant debris and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water 3 at the top several thin ripple beds composed of fine sand are separated by clay drapes they are interpreted as deposits of oscillating currents perhaps a seiche an iridium anomaly 921 23 pg g is observed at the top of the ripple beds our observations at the mimbral locality support the hypothesis of a k t impact on nearby yucatan

some experimental results concerning rapid water table response to surface phenomena abstract a review is made of transient phenomena relating to flow in the vadose zone reviewed topics include rapid water table response to rainfall pulsating flow due to pressure perturbations in the vadose zone and the wave like propagation of increased soil moisture caused by intermittent rainfall as a basis of interpreting these phenomena zoning of the vadose zone into a residual water zone an unsaturated capillary zone and a saturated capillary zone are proposed possible implications with respect to hydrological processes relating to these phenomena are discussed

palaeoenvironments of the permian triassic transition sections in kashmir india abstract detailed measurements of two permian triassic boundary sections at guryul ravine and pahlgam in kashmir indicate continuous sedimentation across the boundary though with a marked change from shallow storm influenced shelf to deeper shelf below wave base successive shell beds through the 2 5 m thick transitional latest permian section at guryul formed as in situ accumulations with little sign of either erosional breaks or condensation faunal change takes place gradually in the late permian transition beds as elsewhere in the tethyan sections there is no major event layer at the permian triassic boundary and little evidence for dysaerobic conditions both the kashmir and east greenland permian triassic sections have sedimentation rates that are orders of magnitude greater than at the condensed meishan reference section they show that the end permian extinction was associated with transgression but not with immediate onset of anoxic conditions macrofaunal extinction seems associated with reduction in primary production which would also explain the dwarfism of fossils found in all permian triassic sections studied so far

snowmelt runoff processes in a headwater lake and its catchment subarctic canadian shield during the snowmelt season surface runoff into northern canadian shield lakes is governed by the distribution of snow and its ablation storage in catchment slopes and valleys and flow delivery from uplands bottomlands and from upper lakes for the lake studied time lags exist between the commencement of snowmelt and the arrival of runoff to the lake with evaporation from the uplands and bottomlands consuming some of the meltwater produced inflow from an upper lake is delayed with all these inputs the lake becomes flooded first forming a moat followed by an expansion of the open water areas which are subject to evaporation loss lake outflow begins when water level rises above the outlet threshold for the snowmelt season outflow constitutes 40 of total melt and rainfall the lake itself is a major storage that continues to maintain outflow until the lake level drops below the threshold in early summer after which flow ceases snowmelt is the main period when runoff is generated from the headwater catchment to replenish storage depleted in the previous summer and to produce flow along the shield valley that contains a chain of lakes copyright 2006 john wiley sons ltd