architecture and evolution of a fjord head delta western vancouver island british columbia the architectural framework and holocene evolution of the zeballos fjord head delta on west central vancouver island was established through a multidisciplinary field based study the zeballos delta is a composite feature consisting of an elevated incised late pleistocene delta and an inset holocene delta graded to present sea level both deltas have a classic gilbert type tripartite architecture with nearly flat topset and bottomset units and an inclined foreset unit time domain electromagnetic tdem and ground penetrating radar gpr surveys borehole data and gravel pit exposures provided information on the internal form lithologies and substrate of both deltas both sets of deltaic deposits coarsen upward from silt in the bottomset unit to gravel in the topset unit the tdem survey revealed a highly irregular buried bedrock surface ranging from 20 m to 190 m in depth and it delineated saltwater intrusion into the deltaic sediments late quaternary sea level change at zeballos was inferred from delta morphology and the gpr survey the elevated late pleistocene delta was constructed when the sea was about 21 m higher relative to the land than it is today it was dissected when sea level fell rapidly as a result of glacio isostatic rebound relative sea level reached a position about 20 m below the present datum during the early holocene foreset beds that overlap and progressively climb in a seaward direction and topset beds that thicken to 26 m landward imply that the delta aggraded and prograded into zeballos inlet during the middle and late holocene transgression sea level may have risen above the present datum during the middle holocene creating a delta plain at about 4 m a s l remnants of this surface are preserved along the valley margins copyright 2004 john wiley sons ltd

observations on delta forming processes in a fjord head delta british columbia canada abstract the bella coola delta is a laterally confined steep fronted fjord head delta in north bentinck arm in the pacific coast mountains of british columbia the principal controls on sedimentation are 1 the high sediment yield and bedload dominance of the bella coola river which reflect climatic conditions and high drainage basin relief 2 river mouth processes which are controlled by tidal stage and delta morphology and 3 delta front deformational processes which are related primarily to oversteepening in the upper delta front wave processes are of limited significance the large tidal range 3 9 m mean range 5 9 m large range changes the location of distributary outlets at high tide and high discharge frictional forces dominate and the effluent disperses as a plane jet over the delta plain at low tide and high discharge inertial frictional and buoyant forces are important and the effluent disperses over saline basin water subaqueous landslides and debris flows have produced a series of erosional chutes on the delta front

gpr in sediments advice on data collection basic processing and interpretation a good practice guide within sedimentological studies ground penetrating radar gpr is being used with increasing frequency because it yields images of the shallow subsurface that cannot be achieved by any other non destructive method the purpose of this paper is to provide an introduction to the collection processing and interpretation of gpr data so that future sedimentary studies can be improved with gpr equipment now being lightweight robust and portable proper data collection and survey design methods need to be followed in order to acquire high resolution subsurface digital data various factors are discussed including reflection profiling velocity soundings test surveys topography logistics data quality and extreme environments basic data processing and visualization are then reviewed followed by a discussion on gpr interpretation strategies including a background to radar stratigraphy for the sedimentary geologist or geomorphologist gpr offers unique data of the shallow subsurface including stratigraphy geometry architecture and structure

late quaternary sediments and geomorphic history of north central vancouver island materials from two glacial and two nonglacial intervals are identified on north central vancouver island british columbia the oldest pleistocene unit muchalat river drift consists of till and overlying glaciolacustrine silt it has been tentatively correlated with dashwood drift of the semiahmoo glaciation an overlying single exposure of mudflow sediment in the gold river valley contains wood dated at 40 900 2000 years bp within the time span of the olympia nonglacial interval the olympia nonglacial interval was characterized by a period of degradation in which olympia age sediments were deposited in transient sedimentary environments and subsequently eroded gold river drift includes gold river advance deposits gold river till and gold river late glacial deposits and was deposited during the fraser glaciation the fraser glaciation was well underway on north central vancouver island by 25 200 330 years bp during the fraser glaciation maximum which occurred after 20 600 330 years bp coast mountain ice flowed in a southwesterly direction across north central vancouver island overtopping all but the highest peaks of the vancouver island mountains deglaciation commenced prior to 12 930 160 years bp and the ice had probably disappeared before 9500 years ago during postglacial times rivers have dissected older quaternary sediments and bedrock up to at least 40 m macroflora data recorded in postglacial lacustrine sediments suggest that the hypsithermal interval commenced before 8300 70 years bp

ground penetrating radar used to assess aggregate in catastrophic flood deposits northeast alberta canada coarse grained aggregate deposited by a catastrophic flood located north of fort mcmurray alberta was examined using ground penetrating radar gpr and lithostratigraphic logging techniques gpr transects were acquired from an upper scoured zone of flood deposits sedimentary structures cross beds and plane beds within the coarse sand and gravel and determinations of depth to bedrock sediment thickness of the aggregate were recognized in the gpr profiles by their varying dielectric properties fine grained conductive underlying oil sand till or glaciolacustrine sediment silt and clay attenuated the radar signal the sedimentary structures mapped from the gpr transects were confirmed in adjacent trench exposures we suggest that gpr is an efficient methodology for determining volumes of aggregate reserves thicknesses of aggregate deposits and mapping sedimentary structures of high energy fluvial sediments key words aggregate ground penetrating radar alberta spillway

detection of subsurface brines freshwater bodies and the interface configuration in between by the time domain electromagnetic method in the dead sea rift israel high radon fluxes in the seismically active dead sea rift seem to be affected by the hydrological system and the different salinities of groundwater bodies involved the time domain electromagnetic tdem method was employed to delineate those different bodies and the configuration of the interfaces between them the present hydrological system and the related brines and interfaces are controlled by the dead sea base level presently at 408 m below msl tdem measurements detect low resistivity 1 ohm m units representing brines and the interface between them as well as the overlying fresher water bodies in addition high resistivity freshwater units are also detected underlying the brines related herein to a multiple hydrological system low resistivity brines detected above the present base level are interpreted herein as yet unflushed ones which correspond to a former higher base level higher sequences below historical sixteenth century base levels are already devoid of brines which gives an indication as to the rate of flushing

river mouth processes in a fjord delta british columbia canada abstract the bella coola delta is a high energy coarse grained fjord delta situated in the coast mountains of british columbia river mouth processes are directly related to the large tidal range 3 9 m mean 5 9 m large which changes the location and nature of distributary mouths producing distinct high tide and low tide outlets frictional forces dominate at high tide as the effluent disperses through five dynamic zones producing a radial bar a friction model applies to this outlet during low tide frictional inertial and buoyant forces and an internal hydraulic jump control the development of six dynamic zones and a lunate middle ground bar a buoyant plane jet model qualitatively best approximates low tide outlet dynamics

appalachian cold air damming abstract appalachian cold air damming is investigated by means of 1 a 50 yr monthly climatology 2 a synoptic case study of the event of 21 23 march 1985 and 3 an investigation of the flow structure and force balance within the cold dome the climatology reveals cold air damming is a year round phenomenon in the southern appalachians with the most frequent prolonged and intense events occurring in winter particularly december and march when three five events per month can be expected cold air damming is least frequent and intense in july the synoptic case study reveals that cold air damming is critically dependent upon the configuration of the synoptic scale flow the cold dome can be identified by a u shaped ridge trough in the sea level isobar thermal patterns and the 930 mb height temperature fields representative of conditions at the base of the inversion overlying the cold dome differential horizontal and vertical thermal advection as well as adiabatic and evaporative cooling are r

the numerical simulation of an unbalanced jetlet and its role in the palm sunday 1994 tornado outbreak in alabama and georgia abstract meso beta scale numerical model simulations and observational data are synthesized in an effort to develop a multistage paradigm for use in forecasting tornadic convection in the southeastern united states the case study to be utilized as an example of the multistage sequence of events is the palm sunday 1994 outbreak which culminates with the development of an unbalanced mesoscale jet streak or jetlet that focuses a given region for significant values of low level vertical wind shear low level confluence and vertical vorticity midtropospheric cooling and storm relative helicity the five stage paradigm includes 1 the existence of a jet exit region accompanying a deep balanced thermally indirect circulation south of the outbreak and a return branch ageostrophic low level southerly jet both typically accompanying the subtropical jet stream and the leading edge of hot continental air 2 the existence of a jet entrance region accompanying a deep balanced thermally direct circulation north of

stable isotopes and debris in basal glacier ice south georgia southern ocean this paper combines a study of the rock debris and d 18 o isotopic characteristics of basal ice sequences in three representative glaciers in south georgia and concludes that the debris and ice has been entrained mainly by basal freezing the size distribution of the rock debris is typical of crushing and abrasion and reflects transport at the ice rock interface the d 18 o relationships show that clear ice associated with the debris has accreted through freezing he white bubbly glacier ice has d 18 o relationships typical of precipitation which demonstrates an altitudinal effect between glaciers

surface mesoscale processes during the 1994 palm sunday tornado outbreak the tornadic storms that developed in the 27 march 1994 palm sunday outbreak were confined to a narrow zone extending from central and northern alabama to western north carolina analysis of surface observations and soundings is used to examine the mesoscale environment of the region starting 14 h prior to storm development the evolution of a shallow front that formed the northern boundary of the outbreak region is tied to several diabatic processes including evaporation of precipitation and differential solar heating the resulting front was found to both limit severe convection and focus supercell development later in the day during the night before the outbreak as copious widespread precipitation fell into dry air evaporation maintained a cold air pool north of the front by contrast moderate southerly flow provided warm moist conditions to the south precipitation enhanced cold air damming along the eastern slopes of the appalachians also may have provided a source of cold air for subsequent frontogenesis over areas farther west during the daylight hours differential solar heating across the front further enhanced frontogenesis intensification of convection just prior to the first tornadoes was found to be associated with areas of breaks in the overcast near and upstream of tornadogenesis similarly cells that intensified were moving over a surface that had been thoroughly moistened by previous rainfall supercells that intersected and moved along the frontal boundary maintained their tornadic strength for many hours whereas storms that crossed the boundary disintegrated blockage of inflow by upstream storm cells may also have contributed to the rapid reduction of intensity of one of the tornadic cells

the role of an apparent mesoscale frontogenetic circulation in squall line initiation abstract a line of severe thunderstorms is observed in satellite imagery to develop explosively from a narrow line of shallow convection at the most rapidly intensifying part of a surface cold front concurrent evaporation of the leading edge of a large area of stratus and stratocumulus clouds behind the front results in the appearance of a mesoscale clear zone adjoining the line convection feature the clear zone enlarges to its maximum width of 65 km less than an hour prior to the genesis of the frontal squall line these observations suggest the possibility that a transverse circulation about the front generated the line convection and clear zone in the upward and downward branches of the circulation respectively and ultimately the squall line analysis of the synoptic surface data indicates the likely presence of a thermally direct frontogenetic circulation at the leading edge of the clear zone the implied frontogenetic process exhibits a rapid e folding time of 3 h corresponding to the develop

mesoscale dynamics in the palm sunday tornado outbreak abstract radar and satellite imagery suggest that strong mesoscale forcing occurred in the palm sunday tornado outbreak on 27 march 1994 parallel lines of severe thunderstorms within each of three mesoscale convective systems developed just ahead of a cold front in mississippi and alabama on this date analyses of routine meteorological observations barograph data and forecasts from the eta and ngm models and a mesoscale research model mass are used to examine the relative roles of large scale dynamics and mesoscale processes in triggering and organizing the mesoscale convection quasigeostrophic forcing was absent in the outbreak region likewise a thermally direct circulation system transverse to the upper level jet that was present to the northwest of the outbreak region was decoupled from the strong low level ascent occurring in northern alabama and mississippi at the time of the outbreak strong ageostrophic frontogenesis in the presence of conditional symmetric instability csi was the chief

seafloor morphology and sedimentary processes knight inlet british columbia seafloor morphology and sediment distribution in knight inlet are discussed as they relate to turbidity currents and associated gravity resedimentation phenomena the study is based on acoustic imagery high resolution seismic profiling echosounding sediment sampling and seabed monitoring seafloor morphology shows that while the upper part of knight inlet resembles other british columbia fjords it differs in that a great many channels emanate from fjord head deltas to coalesce ultimately into a few and finally one channel farther down inlet this is in contrast to the adjacent fjord buteinlet where only one channel emerges opposite each of the two fjord head rivers joining a short distance downslope to form a single incised channel in both fjords sand transporting turbidity currents are responsible for creating these extensive channel systems in knight inlet these channels are up to 40 m deep and up to 300 m wide continuing 41 km down fjord the upper fjord can be divided into four morphological zones which reflect not only the seabed character but also the flow characteristics of turbidity currents using a variety of theoretical techniques based on channel morphology coarsest grain sizes and bedform characteristics turbidity current dynamics were modelled for the seabed morphological zones turbidity current densities are estimated to range from about 1 024 g cm 3 in distal areas to a maximum of 1 048 g cm 3 in the proximal region of greatest erosion and highest velocities average flow velocities are as high as 7 00 m s 1 diminishing to less than 0 50 m s 1 at the terminus of the channel based on estimates of velocity and turbidity current density sediment fluxes were computed for various channel segments changes in flux rates clearly delineated areas of erosion and deposition and were well correlated with the morphological character of the channel and nearby seafloor estimates of turbidity current velocity based on bedform characteristics tend to be lower than those calculated from coarsest grain sizes and channel morphology preserved bedforms may reflect later waning phases of turbidity current flow whereas channel wall heights and coarsest grain size reflect maximum velocities a close relationship was found between turbidity current events as monitored by turbidity event detectors and river discharge peaks on the klinaklini river at the head of the inlet fluvial suspended matter concentrations associated with such floods are not believed to be sufficient to produce turbidity currents directly rather it is postulated that river mouth bars which accumulate during periods of low river flow are destroyed by floods and the coarse sediments along with flood related bedload are swept onto the steep delta front where they accumulate as temporary unstable sediment masses failing occasionally or continue directly downslope as debris flows turbidity currents

the impact of the appalachian mountains on cyclonic weather systems part i a climatology abstract a climatological study of cold fronts and cyclones crossing the appalachian mountains from the west through northwest has been performed a sample size of 50 fronts and 40 cyclones was derived from the seven winter seasons december through march between 1979 and 1986 the analysis revealed that initially linear cold fronts are slowed and deformed by the mountains with the mean frontal speed decreasing 40 and the fronts developing a pronounced kink just east of the southern appalachians furthermore over the mountains the cross front thermal and pressure gradients are enhanced by about 25 and 63 respectively once past the mountains fronts are weaker and often difficult to locate in particular the cyclonic wind shift is very ill defined and the cross front pressure gradient is reduced to 38 of the premountain value finally small scale 500 km diameter lee lows form on more than half of the fronts though typically benign some of these disturbances may play a role in offshore c

transient electromagnetic sounding for groundwater the feasibility of using the transient electromagnetic sounding ts or tdem method for groundwater exploration can be studied by means of numerical models as examples of its applicability to groundwater exploration we study four groundwater exploration problems 1 mapping of alluvial fill and gravel zones over bedrock 2 mapping of sand and gravel lenses in till 3 detection of salt or brackish water interfaces in freshwater aquifers and 4 determination of hydrostratigraphy these groundwater problems require determination of the depth to bedrock location of resistive high porosity zones associated with fresh water determination of formation resistivity to assess water quality and determination of lithology and geometry respectively the ts method is best suited for locating conductive targets and has very good vertical resolution unlike other sounding techniques where the receiver transmitter array must be expanded to sound more deeply the depth of investigation for the ts method is a

basin sedimentation and the growth of prograding deltas a theoretical model is developed for the infilling of a basin by the progradation of a delta the model simulates four mechanisms for the transfer of sediment from the land to the sea 1 bed load dumping along the delta front 2 hemipelagic sedimentation under the seaward flowing river plume 3 proximal slope bypassing by turbidity currents and 4 the combined effects of both short term wave and tidal action and long term creep and small slides downslope diffusion of the accreting sediment mass the general model is of relatively low precision useful for predicting basin infilling on time scales greater than a few hundred years the river plume portion of the model can predict sedimentation on time scales of less than a year and is designed to reflect the dynamics of a free two dimensional buoyant jet that transports a composite size population of suspended particles the general model allows the prediction of lithologies changing with time and space the model has been used to simulate infilling processes for knight and bute inlets two grabenlike fjord basins along the coast of british columbia model simulations of delta progradation over the last 10 000 years favorably predicted the modern seafloor bathymetry and sediment accumulation rates to within a factor of 2 of measured 210pb 137cs and sediment trap rates

jetlet formation from diabatic forcing with applications to the 1994 palm sunday tornado outbreak abstract the three dimensional responses of simple stably stratified barotropic and baroclinic flows to prescribed diabatic forcing are investigated using a dry hydrostatic primitive equation numerical model the north carolina state university geophysical fluid dynamics model a time dependent diabatic forcing is utilized to isolate the effects of latent heat release in a midlatitude convective system examination of the mass momentum adjustments to the diabatic forcing is performed with a focus on the development of an isolated midlevel wind maximum the results of both cases suggest the formation of a midlevel wind maximum in the form of a perturbation meso scale cyclone which later propagates downstream as the heating is decreased the scale of the perturbation cyclone remains at a sub rossby radius of deformation length scale therefore the mass perturbations adjust to the wind perturbations as the mesocyclone propagates downstream transverse vertical circulations which favor ascent on the r

imaging the subsurface stratigraphy in the ubehebe hydrovolcanic field death valley california using ground penetrating radar abstract ground penetrating radar gpr surveys were carried out to collect subsurface images of the basaltic base surge deposits in the ubehebe hydrovolcanic field death valley national park california antennae with frequencies of 50 100 and 200 mhz were used this technique allowed the collection of useful geologic data for example the lower stratigraphic boundary of the pyroclastic deposits can be imaged and their thickness can be estimated different radar responses were also obtained from base surge deposits and underlying sedimentary rocks which enable their recognition where no outcrops are available furthermore gpr data confirmed the presence of small eroded craters which are partially filled by alluvium in this case an unconformity between the overlying horizontally bedded alluvium and the underlying bowl shaped base surge deposits can be recognized within the crater and the thickness of the alluvium estimated common mid point cmp surveys suggested subsurface velocities of the electromagnetic waves in the upper part of these deposits between 0 095 0 1 m ns