rates and possible causes of neotectonic vertical crustal movements of the emerged southeastern united states atlantic coastal plain emerged pliocene and pleistocene shorelines and associated marine deposits were used to determine the magnitude and rate of vertical crustal movement during the past 3 m y in the united states atlantic coastal plain of south and north carolina on the basis of a new regional ostracode assemblage zonation planktic biostratigraphic data and radiometric data emerged marine deposits were determined to be primarily interglacial and can tentatively be correlated with hemispheric warm intervals in evidence from deep sea data the paleontologic evidence indicates a primary glacio eustatic component to the local sea level record and a secondary tectonic component net vertical uplift rates averaging 1 to 3 cm 1 000 yr but perhaps as high as 5 to 10 cm 1 000 yr are in evidence for the emerged coastal plain although details of the timing of regional rheological events remain obscure the trend of net uplift contrasts with general subsidence rates of about 2 to 4 cm 1 000 yr since the cretaceous in submerged parts of the continental margin near subsiding sedimentary troughs hydro isostatic crustal response to multiple deglaciation events may have periodically uplifted the coast but long term lithospheric flexural upwarping in response to sediment loading offshore is a more plausible mechanism to explain the present positions of shorelines above present mean sea level a eustatic sea level model is proposed for interglacial high stands of the past 3 0 m y

vertical sequence and lateral transitions in the facies of a barred nearshore environment abstract nine tube cores 7 cm in diameter and up to 150 cm long from a nearshore crescentic bar in kouchibouguac bay new brunswick canada reveal the vertical sequence and lateral transitions of facies previously identified only in shallow box cores the facies are a inner shelf shoreface transition bioturbated fine sands and silts with remnant primary structures b seaward slope planar lamination in medium to fine sands dipping gently seaward and composite bed sets of planar to ripple cross lamination in fine sand chevron lamination is rare c bar crest low angle planar lamination dipping both landward and seaward and medium scale trough cross lamination in medium to coarse sands d landward slope planar lamination dipping landward with small scale la dward dipping trough cross lamination occasionally small to medium scale trough cross lamination is found with seaward dips e trough massively bedded lags of coarse gravelly sands with abundant shell fragments contrast with isolated very thin units of massive silt and units of well sorted sands the latter display subhorizontal planar lamination and small to medium scale trough cross lamination polymodal dips indicate bed form migration landward alongshore and offshore vertical sequences and lateral transitions seaward of the bar crest suggest that three wedge shaped units inner shelf shoreface transition seaward slope bar crest interdigitate in an offlap onlap sequence to landward the trough and landward slope facies interfinger complexly while the crest facies forms a simple onlap over landward slope facies total reworking of sediments within the bar trough system is expected every 5 to 6 years and long term preservation is limited to the inner shelf shoreface transition seaward slope and trough facies

atmospheric and depositional environments traced from unique chemical compositions of the snow over an inland high plateau antarctica surface snow samples from the inland high plateau east queen maud land antarctica show unique chemical characteristics they are characterized by high acidity accompanying the high electrical conductivity so that the hydrogen ion is the dominant ion coupling with chloride and nitrate ions the chemical composition differs sharply from sea salts these characteristics appear more clearly than previously reported in antarctica and are most strongly developed in snow samples from the high region the tritium content increases in the inland high area especially in the region higher than 3600 m asl above sea level which corresponds to the region where the effects of katabatic wind have vanished in the glaciological observations the highest tritium content occurs in the vertical profile at a snow pit 3761 m asl 77 00 s 35 00 e which corresponds to the snow deposition in 1966 the concentration is the highest ever reported in antarctica and is almost as high as the one observed in the precipitation in the inland region of north america which is the highest value ever reported in the world all the results suggest that most of the ions contained in snow samples from the inland high plateau especially higher than 3600 m asl are not brought directly through the troposphere from the sea around antarctica but from the higher atmosphere and that they are under the influence of the physicochemical reactions occurring there

shelf construction in a foreland basin storm beds shelf sandbodies and shelf slope depositional sequences in the upper cretaceous mesaverde group book cliffs utah the upper cretaceous campanian kenilworth member of the blackhawk formation mesaverde group is part of a series of strand plain sandstones that intertongue with and overstep the shelfal shales of the western interior basin of north america analysis of this section at a combination of small sedimentological and large stratigraphical scales reveals the dynamics of progradation of a shelf slope sequence into a subsiding foreland basin four major lithofacies are present in the upper mancos and kenilworth beds of the book cliffs a lag sandstone and channel fill shale lithofacies constitutes the thin basal transgressive sequence which rests on a marine erosion surface it was deposited in an outer shelf environment shale interbedded sandstone and shale and amalgamated sandstone lithofacies were deposited over the transgressive lag sandstone lithofacies as a wave dominated delta and its flanking strand plains prograded seaward analysis of grain size and primary structures in kenilworth beds indicates that there are four basic strata types which combine to build the observed lithofacies the fine to very fine grained graded strata of the interbedded facies are tempestites deposited out of suspension by alongshelf storm flows geostrophic flows there is no need to call on cross shelf turbidity currents density underflows to explain their presence very fine to fine grained hummocky strata are likewise suspension deposits created by waning storm flows but were deposited under conditions of more intense wave agitation on the middle shoreface cross strata sets in this region are bed load deposits that accumulated on the upper shore face in the surf zone lag strata are multi event bed load deposits that are the product of prolonged storm winnowing they occur on transgressive surfaces while the graded beds are tempestites in the strict sense all four classes of strata are storm deposits the distribution of strata types and their palaeocurrent orientations suggests a model of the kenilworth transport system driven by downwelling coastal storm flows and probably by a northeasterly alongshore pressure gradient the stratification patterns shift systematically from upper shoreface to lower shoreface and inner shelf lithofacies partly because of a reduction in fluid power expenditure with increasing water depth but also because of progressive sorting which resulted in a decrease in grain size in the sediment load delivered to successive downstream environments the kenilworth member and an isolated outlier the hatch mesa lentil constitute a delta prodelta shelf depositional system their rhythmically bedded lenticular sandstone and shale successions are a prodelta shelf facies and may be prodelta plume deposits major upper cretaceous sandstone tongues in the book cliffs are underlain by erosional surfaces like that beneath the blackhawk formation which extend for many tens of kilometres into the mancos shale these surfaces are the boundaries of upper cretaceous depositional sequences the sequences are large scale genetic stratigraphic units they result from the arranging of facies into depositional systems the depositional systems are in turn stacked in repeating arrays which constitute the depositional sequences the anatomy of these foreland basin sequences differs

groundwater surfacewater interactions at the transition of an aquifer from unconfined to confined a three dimensional numerical model is developed to identify systematic changes in the interactions between the groundwater flow systems and streams that cross the transition zone where unconfined aquifers become confined a generalized model is designed that represents hydrologic conditions where gently dipping aquifer confining unit sedimentary sequences subcrop beneath a thin surficial aquifer and are transected by gaining streams flowing parallel to dip a series of simulations are performed to investigate the effect of different hydrogeologic characteristics of the edge of the confining unit where potential for facies changes or fluvial reworking results in variations in the material properties of the confining unit the results show an abrupt increase in groundwater discharge to the stream immediately upstream of the transition to confined conditions and a corresponding but not equal decrease in groundwater discharge along stream reaches downstream of the edge of the confining unit model results were compared to measured stream discharges at a location where the loosahatchie river of eastern tennessee usa crosses an unconfined confined transition in the upper mississippi embayment

resolving aquifer behavior near a focused recharge feature based upon synoptic wellfield hydrogeochemical tracer results aquitard windows are known to occur in unconsolidated aquifer systems and represent areas offocused recharge to otherwise confined underlying aquifers the study herein focused on a known window site affecting the memphis aquifer located in the sheahan wellfield in shelby county tennessee uranium and thorium series radioisotopes were evaluated from production wells sampled in the wellfield and compared to other geochemical characteristics of the system from the research a conceptual model was realized whereby higher uranium concentrations from near surface waters flow through a redox barrier in the aquitard window and become depleted in uranium further 234 u 238 u activity ratio increased downgradient of the recharge source by alpha recoil mobilization of 234 u via 234 th and possibly leaching of uranium bound by iron hydroxides via dissolution and subsequent precipitation by reducing waters flowing to downgradient wells the behavior of the hydrogeochemical tracers could be best described in the conceptual model by normalizing uranium to fe 2c throughout the system the use of the u fe 2c pair provides a useful tool for understanding of the mixing behavior near focused recharge sites with redox barriers and may be useful for developing aquifer behavior models q 2005 elsevier b v all rights reserved

sedimentology ichnology and paleoenvironments of the upper cretaceous wenonah and mt laurel formations new jersey abstract the wenonah and mt laurel formations of the new jersey coastal plain comprise a shallow subtidal coarsening upward regressive sequence that accumulated along a wave dominated coast in late cretaceous maestrichtian time the highly bioturbated muddy very fine to fine quartz sands of the wenonah formation were deposited mainly in the offshore zone of an inner shelf below storm wave base distinctive trace fossils include rosselia socialis and a planar form of zoophycos the mt laurel formation consists of two lithofacies in the northern new jersey coastal plain the formation is characterized by burrowed clean quartz sands that are thinly interbedded with muddy sand and mud characteristic trace fossils include ophiomorpha nodosa rosselia socialis two forms of skolithos and a delicate branching burrow deposition occurred mainly in the offshore shoreface transition zone between fair weather and storm wave base storm deposits include burrowed sands displaying trough cross stratification hummocky cross stratification lenticular and wavy ripple bedding and parallel lamination fair weather deposits consist of thoroughly bioturbated muddy sand and thin bedded mud at updip exposures shoreface deposits include trough cross strati ied burrowed fine to medium sands paleocurrents were bipolar with a predominant northwest onshore mode a massive sand lithofacies characterizes the mt laurel formation in the central and southern new jersey coastal plain and is characterized by highly bioturbated medium to coarse sand rare cross stratification indicates a polymodal paleocurrent pattern with predominantly northwest transport distinctive trace fossils include ophiomorpha nodosa and skolithos linearis this lithofacies accumulated mainly as shoals or bars in the transition and offshore zones of the inner shelf a shoreface ebb tidal delta facies was locally developed the marshalltown wenonah and mt laurel formations comprise a depositional sequence in the sense of haq et al 1987 that accumulated during a third order eustatic sea level cycle uza 4 4 the wenonah mt laurel regression occurred during a sea level high stand as sediments began to overflow estuaries created during the marshalltown transgression subsequent falling sea level intensified the regression and ultimately led to erosional truncation of the mt laurel sediments then eustatic rise in sea level during the late maestrichtian uza 4 5 led to ravinement during this ravinement event a fossiliferous and pebbly glauconitic quartz sand lithofacies was deposited as a transgressive lag in the transition and offshore zones of the inner shelf these transgressive sheet sand ediments comprise the lower part of the navesink formation the depositional model developed herein for the wenonah mt laurel regressive interval integrates both sedimentologic and ichnologic data this model is compared with the well known gallup and blackhawk cretaceous regressive sequences of the north american western interior it should be applicable in the evaluation of other regressive sequences in cretaceous strata of the u s atlantic coastal plain and western interior as well as epeiric sea cycles from other similar settings around the world

evolution of a classic sand ridge field maryland sector north american inner shelf the ridge and swale topography of the middle atlantic bight is best developed on the delaware maryland inner shelf here sand ridges can be seen in all stages of formation several aspects of the ridge field are pertinent to the problem of ridge genesis the first is ridge morphology there is a systematic morphologic change from shoreface ridges through nearshore ridges to offshore ridges which reflects the changing hydraulic regime as successively more seaward ridges are examined maximum side slope decreases the ratio of maximum seaward slope to maximum landward slope decreases and the cross sectional area increases these changes in ridge morphology with depth and distance from shore appear to be equivalent to the morphologic changes experienced by a single ridge during the course of the holocene transgression a second aspect is the change in bottom sediment characteristics that accompanies these large scale morphologic changes megaripples sand waves and mud lenses appear in the troughs between nearshore and offshore ridges these changes indicate that the storm flows which maintain ridges are less frequently experienced in the deeper sector and that the role of high frequency wave surge becomes less important relative to the role of the mean flow component in shaping the sea floor a third aspect is the systematic relationship of grain size to topography grain size is 90 out of phase with topography so that the coarsest sand lies between the axis of the landward trough and the ridge crest while the finest sand lies between the ridge crest and the axis of the seaward trough this relationship is characteristic of large scale bedforms finally flow was measured and transport calculated on the same ridge during a one month period november 1976 threshold was exceeded only during storm events mean transport was southerly and a little seaward with respect to both the ridge crest and the shoreline these flow measurements are in conformity with the pattern of smaller bedforms a 43 year time series of bathymetric change for this ridge reveals a systematic pattern of landward flank erosion seaward flank deposition and seaward crest migration sand ridges are considered the consequence of constructive feedback between an initial topography and the resulting distribution of bottom shear stress the relationship between grain size and topography supports this model but does not account directly for the oblique angle of the ridge with respect to the coastline this feature may be due to a more rapid alongshore migration rate of the inshore edge of the ridge than the offshore edge and the relationship between this migration rate and the rate of shoreface retreat

depositional processes on an ancient and modern muddy shelf northern california the modern eel river shelf and analogous pleistocene rio dell formation in northern california provide an ideal opportunity to combine the advantages of studying a modern environment with those of studying an ancient sequence and thereby enables further understanding of muddy shelf processes the modern shelf is the site of accumulation of a thick deposit of holocene mud both large scale sediment distribution patterns and small scale stratigraphy on the shelf indicate that river floods play an important role in sediment accumulation even on a high energy storm dominated coast the major factors in preservation of this flood signature are the cohesive behaviour of fine grained sediments and episodically rapid rates of sediment input the rio dell formation includes approximately 400 m of mostly fine grained shelf deposits that accumulated offshore from a palaeo eel river mouth the shelf sediments comprise four depositional sequences sequence 1 records progradation from outer to inner shelf depths facies trends closely resemble across shelf trends on the modern shelf suggesting that processes were similar detailed examination of these deposits provides insight into the nature and role of various processes on both the ancient and modern shelf muddy facies of the rio dell sequence are characterized by bioturbated clayey silts interbedded with event layers of several types clay rich silt layers are interpreted as flood deposits and physically stratified coarse silt layers are interpreted to record transport and deposition of coarse silt on the midshelf during storms sediment transport calculations and consideration of grain size distributions of bioturbated sediments which form the bulk of the rio dell sequence suggest that these sediments are the result of biological homogenization of the fine grained flood deposits and of the coarser grained storm deposits the results of this study in general indicate that fine grained shelf deposits do preserve a distinguishable if subtle record of depositional processes

facies architecture and sequentiality of nearshore and shelf sandbodies haystack mountains formation wyoming usa the haystack mountains formation campanian mesaverde group us western interior basin wyoming contains a series of shallow marine sandbodies extending tens of kilometres out from a basin margin the study succession around 200 m thick is composed of eight major sandstone tongues bolten ranch o brien spring seminoe 1 2 3 4 hatfield 1 and 2 members each partially encased within marine shale intervals the formation is sequential at several scales at the largest scale the whole succession presents an aggradational to basinward stepping stacking pattern of the sandstone tongues at a lower level each tongue member is characterized internally by two different types of lithosome the first represents shoreface progradation with hummocky cross strata passing up to swaley and trough cross stratified sandstones this lithosome is erosively truncated at its top in most cases and has a general sheet like geometry along strike whereas down dip it displays a series of sharp bounded clinothems the latter sometimes indicate a downward as well as a basinward shift through time as suggested by the occurrence of coarser and or shallower facies at a lower level in the shoreface profile the second type of lithosome is sheet or wedge like and sharply overlies the shoreface deposits the lithosome consists of laterally widespread units of planar tabular to trough cross bedded medium sandstones passing laterally in a dip direction into bioturbated sandstones the lower part of this lithosome is progradational becoming retrogradational into the overlying shales the facies within the cross bedded lithosome suggest a tidally dominated delta front to estuarine depositional setting the two types of lithosome are not related genetically the erosion surface separating the two lithosomes is a sequence boundary separating forced regressive relative sea level fall shoreface deposits from lowstand to transgressive early relative sea level rise cross bedded deposits the uppermost part of the cross stratified lithosome shows a landward stepping of component parasequences and is abruptly blanketed by open marine shales the most widespread cross bedded lithosomes are apparently best developed in the lowermost members of the haystack mountains formation i e in the aggradational part of the large scale progradational succession in the uppermost highly progradational sandstone tongues the shoaling upward shoreface lithosome dominates whereas the cross bedded lithosome occurs in narrow lensoid belts or is absent the middle portion of the succession shows intermediate characteristics the vertical variation in geometry thickness and progradational extent of successive cross bedded lithosomes results from greater confinement of the incised nearshore systems both in space landward direction and in time from the aggradation to the progradation architecture the latter is a consequence of a decreasing rate of accommodation creation through time

reconstruction of paleo wave conditions during the late pleistocene from marine terrace deposits monterey bay california the santa cruz coastal terrace fringes much of the northern monterey bay region california it consists mainly of a regressive sequence of high energy barred nearshore marine sediments deposited during the last sangamonian highstand of sea level this sequence can be sub divided into several depth dependent facies on the basis of paleo current data and vertical sequence of sedimentary structures these include a lower shoreface facies deposited in 10 16 m water depth an upper shoreface facies including both a storm dominated assemblage and a surf zone assemblage deposited in 0 10 m water depth and a foreshore facies deposited in the swash zone up to 3 5 m above high tide the magnitudes of the storm events responsible for depositing these sediments were estimated by calculating paleo wave heights using a variety of criteria e g critical threshold equations breaker depths berm heights in addition the climate and paleogeography during the deposition of these sediments were essentially the same as today allowing the use of present day wave statistics to estimate the frequency of these storm events the largest storms formed offshore flowing currents e g rip wind forced and possibly storm surge ebb currents that resulted in the deposition of approximately 30 of the sediments seaward of the surf zone however the magnitude and frequency of these events are unknown the remaining 70 of the sediment beyond the surf zone was deposited in response to smaller storm waves which were on the average at least 1 6 m high such waves presently occur no more than 15 of the time sediments deposited during fairweather conditions i e the remaining 85 of the time have a low preservation potential and are generally not preserved in this facies in contrast surf zone sediments were deposited by a variety of processes associated with waves whose maximum offshore heights were probably 2 2 m such waves presently occur up to 92 of the time sediments within the swash zone were deposited by waves up to 3 m high the largest of which presently occur approximately 2 of the time most of the sediments were deposited by storms of intermediate magnitude and frequency different facies however appear to preferentially record events of different recurrence intervals in particular surf zone sediments were deposited under relatively small storm and post storm conditions whereas sediments deposited farther offshore record increasingly larger less frequent storm events relatively rare events e g the 100 or 1000 yr events do not appear to have significantly affected sedimentation in these nearshore environments

thin fine grained storm layers in a muddy shelf sequence an example from the lower jurassic in the stenlille 1 well denmark thin storm sand layers are a characteristic feature of many sandy shelf sequences while little evidence of storm layers is preserved in muddy shelf deposits where bioturbation is often total the present study shows that storm generated depositional processes governed sedimentation in a muddy shelf environment the studied sequence is dominated by blackish mudshale and silt streaked mudshale with thinner intervals of pale fine grained heterolithic sandstone it represents the lower jurassic fjerritslev formation in the eastern part of the danish basin and has been studied in four cores from the stenlille 1 well within the muddy outer shelf association four sedimentary facies and 14 types of laminae 0 5 10 mm thick may be distinguished most of the laminae share the characteristics of graded bedding erosive bases and occasional fading ripples with storm layers of sand grade the structures indicate that the mudshale laminae formed by settling of the suspension load carried by storm generated currents this kind of episodic deposition of fine grained storm layers may be common though rarely preserved in outer shelf environments

near surface wetting of a ponded basalt surface observations using time domain reflectometry abstract the changes in dielectric constant k a during an infiltration test on a fractured basalt surface in south eastern idaho were monitored using time domain reflectometry tdr because changes in k a were caused largely by changing amounts of water in the formation and to a small extent by diurnal and seasonal temperature fluctuations tdr served as a useful indicator of the moisture status in the formation our results indicate that wetting and drying were spatially variable within and immediately beyond a 7 8 m 2 pond various locations close to the surface responded to fast flow whereas others showed evidence of poor hydraulic communication with the surface data collected during a rainfall event which occurred a few days after ponding ceased indicated that this boundary condition evoked a similar hydrologic response to ponding this effort suggests that tdr is a useful tool for detecting moisture changes in fractured media

correlation of a 3 200 year old tephra in ice cores from vostok and south pole stations antarctica tephra layers in two antarctic ice cores are correlated on the basis of their chemical compositions and estimated ages we believe the tephra was produced about 3 200 years ago from a major explosive eruption of candlemas island in the south sandwich islands this is the first time that tephra layers have been correlated between two widely separated ice cores and demonstrates that tephra layers may serve as stratigraphic markers for correlating and perhaps in some cases dating antarctic ice cores

eocene biostratigraphy of south carolina and its relationship to gulf coastal plain zonations and global changes of coastal onlap an assimilation of mega invertebrate assemblages in south carolina with gulf coast biozones allows for the subdivision of the middle and late eocene into four regional zonations that can be compared with proposed global sequences controlled by eustatic changes of sea level the middle eocene can be divided in ascending stratigraphic order into the cubitostrea perplicata zone c lisbonensis zone and c sellaeformis zone the late eocene is represented by the crassatella alta chlamys cawcawensis zone these zones are separated by type 1 or type 2 unconformities that bracket global sequence boundaries unconformity types after vail and todd 1981 the following sequences are proposed for the middle and upper eocene te2 1 cubitostrea perplicata zone followed by a type 2 unconformity te2 2 c lisbonensis zone followed by a type 2 unconformity te2 3 c sellaeformis zone followed by a type 1 unconformity and te3 crassatella alta chlamys cawcawensis zone followed by a type 2 unconformity although not recognized in the downdip areas of south carolina the te3 sequence can be further subdivided into a te3 1 sequence and te3 2 sequence separated by a type 2 unconformity this regional break lies at the gosport sand lower moodys branch formation upper moodys branch formation contact in the gulf coastal plain and at the base of the tivola tonque in georgia

preservation and grain size trends of holocene wave dominated facies successions in eastern japan implications for high resolution sequence stratigraphic analysis vertical grain size trends provide significant information for the sequence stratigraphic analysis of siliciclastic wave dominated facies successions this paper discusses the relationships between the preservation timing and the grain size trends of holocene wave dom inated successions in two contrasting coastal plains the kujukuri and sendai using high resolution ams 14 c dating depositional facies and grain size modal grain size is proposed as a good criterion for eval uating qualitative changes of depositional depth the kujukuri and sendai successions are both fining upward to coarsening upward wave dominated successions that have developed upon ravinement surfaces the fining upward part of the kujukuri succession formed in regressive deposits during a highstand period whereas that of the sendai formed during transgression a difference in the timing of the generation of upward fining is due to the varying preservation potential of transgressive shoreface deposits on the ravi nement surface in the sendai area the potential was much higher than in the kujukuri area because the sendai ravinement surface had re ceived greater sediment supply from the adjacent rivers during trans gression a differing rate of tectonic uplift between the areas was not critical to the preservation potential because of the short time scale the successions show bimodal grain size distributions in the basal parts and unimodal distributions elsewhere the bimodality is consid ered to be the result of mixing of a coarse transgressive lag with finer sediment derived from external sources the finer mode forms a con sistent trend with unimodal grain sizes in overlying deposits the trend is of a simple upward coarsening in the kujukuri and an upward fining to coarsening in the sendai showing distinctive correlation with chang es of depositional depth thus the vertical trend of the modal grain size and not mean or median is best for evaluating changes of de positional depth in ancient wave dominated facies successions

recognition and hydrologic significance of passive margin updip sequences an example from eocene coastal plain deposits u s a abstract sequence stratigraphic interpretations are extended to a passive margin updip setting using sedimentological observations from cores and well to well correlations in eocene coastal plain strata of south carolina in the succession studied formation contacts tend to follow sequence boundaries even as lithologies vary within individual sequences sequence boundaries at the base of the congaree formation and near the top of the tinker formation formed during relative sea level fall associated with second order global cycles these boundaries can be recognized clearly in both downdip and updip areas of the passive margin three other sequence boundaries which occur at the base and top of the warley hill formation and within the tinker formation are interpreted as formed during relative sea level fall associated with third order global cycles hydrostratigraphic units in the strata studied conform to depositional patterns that were controlled by changes in sea level and sediment influx sand of the gordon aquifer comprises a thick aggradational succession deposited predominantly in the nearshore shelf environment as accommodation increased during relative rise in sea level because of high rates of sedimentation in the proximal setting aggradational stacking of nearshore sands may be common to other updip marine strata in accommodation dominated regimes the overlying gordon confining unit consists of marine shelf clay and carbonate sediment deposited in response to maximum transgression during subsequent relative sea level fall accumulation of shoreface deposits produced a progradational succession that is represented by the lower part of the upper three runs aquifer unlike formation contacts boundaries between the clastic aquifers and confining units do not follow the third order sequence boundaries because of lithologic variations within the sequences an increasing degree of breaching through the gordon confining unit which results in downward contaminant migration into the gordon aquifer occurs in the updip direction because of nearly continuous sand deposition near the base of the interval studied contaminants migrate locally through the crouch branch confining unit because of erosional breaches formed by scour during sea level lowstand in this example and in other strata deposited in an updip passive margin setting the extent to which confining units are breached at sequence boundaries decreases in the downdip direction resulting in better protection of the adjacent aquifer

storm features of siliciclastic shelf sedimentation in the mid cretaceous epeiric seaway of northern australia abstract late aptian to early cenomanian strata were deposited in a large epeiric seaway which covered much of the northern australian landmass during mid cretaceous time the seaway stretched from the carpentaria basin in the north to the eromanga basin in the south during this period siliciclastic sediments accumulated on a gently sloping epeiric shelf which formed the western margin of the carpentaria basin the shelf maintained a relatively similar configuration throughout the mid cretaceous with water depths rarely exceeding 50 m and the seafloor was apparently within the influence of storm waves over much of the area the shelf was storm and wave dominated and most early formed or fair weather sedimentary structures were destroyed or extensively modified during episodic storms storm features include hummocky cross stratification shelly lags erosional conglomeratic lags gutter casts lenticular micro hummocky sand beds megaripples characteristic low diversity and opportunistic ichnofacies various styles of wave ripple lamination and poorly preserved event beds most storm influenced units are preserved as coarsening and shallowing upwards facies successions which aggraded during high relative sea level and prograded during falling relative sea level some of these successions were subsequently eroded during further cyclic fluctuations of relative sea level

sedimentology and depositional environments of middle eocene terrigenous carbonate strata southeastern atlantic coastal plain usa abstract basin margin sediments of middle eocene age in the savannah river site area consist of five terrigenous carbonate lithofacies quartz sand calcareous quartz sand sandy carbonate muddy carbonate and a transitional lithofacies that ranges from sandy muddy carbonate to calcareous mud the middle eocene sediment package which includes calcareous parts of the upper congaree warley hill and santee formations dips southeast at 4 7 m km and thickens from 2 m at its updip edge to 95 m downdip the presence of glauconite and a diverse faunal assemblage in all lithofacies suggests deposition in clear well oxygenated open marine waters of normal salinity on the inner to middle shelf with periods of marginal marine nearshore and deltaic influence coarse grained terrigenous sand and calcareous sand deposited in higher energy nearshore environments occur near the updip limit fine grained terrigenous mud calcareous mud and sandy and muddy carbonate are located downdip and accumulated in quieter water conditions on the inner and middle shelf the transition from terrigenous to carbonate sediment occurs near the updip limit in a narrow zone less than 5 km wide three depositional sequences which contain transgressive and highstand system tracts are recognized within the middle eocene calcareous interval one is assigned to the upper congaree formation ta 3 5 3 6 cycles the main control on areal distribution hill formation ta3 4 cycle and one to the santee formation ta 3 5 3 6 cycles the main control on areal distribution of facies was depositional environment which was controlled primarily by sea level eustasy and the amount rate and locus of terrigenous influx in updip areas however sediment distribution and thickness were also influenced by middle eocene growth faulting diagenetic pathways vary with facies type but generally include 1 marine phreatic boring of skeletal fragments by algae and fungi grain micritization and radially fibrous cementation and 2 freshwater phreatic inversion of high mg calcite to low mg calcite dissolution of aragonitic allochems formation of moldic porosity precipitation of syntaxial calcite overgrowths on echinoderms formation of calcite spar and isopachous calcite cement neomorphism of micrite to microspar and pseudospar precipitation of opal ct lepispheres replacement of mollusk shells by chalcedony and precipitation of zeolites within secondary moldic pores quartz rich facies have high interparticle porosity and excellent permeability mud rich facies have low to moderate porosity and permeability owing to the isolation of moldic and vug pores

efficacy of genetic algorithm to investigate small scale aquitard leakage the movement of water from a shallow aquifer to a semiconfined aquifer through a localized area of leakage in an aquitard designated as an aquitard window is an area of concern in certain gulf coastal plain aquifer settings locating these windows or areas of leakage has been historically arduous the purpose of this study was to evaluate the use of a genetic algorithm ga technique as an inverse technique for locating highly probable areas of leakage based upon aquifer head data near the suspected area of leakage the ga technique has previously been tested on synthetic data alone and this research offers insight into the capabilities of the technique with actual field data from a site with a known aquitard window research sites with historical and ongoing data collection efforts are rare and offer the best opportunity for robust evaluation of new methodologies based upon the ga technique the steady state accretion flux to the memphis aquifer at the shelby farms study site was determined to be 12 346 m day with a standard deviation of 821 m day and compared well with the range from 510 to 9 911 m day previously determined for the site