optically stimulated luminescence age controls on late pleistocene and holocene coastal lithosomes north carolina usa luminescence ages from a variety of coastal features on the north carolina coastal plain provide age control for shoreline formation and relative sea level position during the late pleistocene a series of paleoshoreline ridges dating to marine isotope stage mis 5a and mis 3 have been defined the kitty hawk beach ridges on the modern outer banks yield ages of 3 to 2 ka oxygen isotope data are used to place these deposits in the context of global climate and sea level change the occurrence of mis 5a and mis 3 shorelines suggests that glacio isostatic adjustment gia of the study area is large ca 22 to 26 m as suggested and modeled by other workers and or mis 3 sea level was briefly higher than suggested by some coral reef studies correcting the shoreline elevations for gia brings their elevation in line with other sea level indicators the age of the kitty hawk beach ridges places the holocene shoreline well west of its present location at ca 3 to 2 ka the age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast usa suggesting some regionally contemporaneous forcing mechanism

history of stage 5 sea level in bermuda review with new evidence of a brief rise to present sea level during substage 5a abstract oxygen isotope substage 5e is represented by the devonshire formation in bermuda the occurrence of these coastal marine deposits to about 5 m indicates pleistocene sea level data in bermuda do not need tectonic corrections a few published u series coral dates suggest that a conglomerate spencer s point formation may have formed during substage 5c geologic mapping however indicates that the eolianite beneath the conglomerate is pre rather than post devonshire formation in age as was previously thought and the aminostratigraphy of marine sheels also confirms the correlation of the spencer s point and devonshire formations substages 5c and 5a are represented by the southampton formation large eolianites comprise the bulk of this formation they are onlapped by a few small younger marine 1 m and eolian deposits aminostratigraphy confirms that these late southampton age deposits are significantly younger than the devonshire formation and u series dates indicate a substage 5a age the setting of some of these deposits along a protected shoreline precludes discounting their position as anomalous due to large storms this evidence that sea level in bermuda was at about present datum late in substage 5a agrees with interpretations of neotyrrhenian deposits of mediterranean shorelines but not with inferences from the deep sea oxygen isotope record or with data from uplifted coral reefs

south carolina interglacial sites and stage 5 sea levels abstract amino acid and other studies have been made on the 30 km pleistocene sections of the intracoastal waterway between myrtle beach and little river south carolina our ratios differentiate the long established waccamaw oldest canepatch and socastee formations the ratios from the four laboratories that have worked in this area agree very well and apparent conflicts with u series dates may merely reflect an abundance of reworked corals our amino acid correlations with u series coral dates in south carolina bermuda and the mediterranean all argue that the classical canepatch and its horry clay date from isotope stage 5e and not as has been implied from stage 7 9 11 or 13 excavations and erosion have increased position fixing problems along the waterway and canepatch amino acid ratios and u series dates 460 000 100 000 yr b p at icw5 may be from an older unit the canepatch shows the double marine transgression visible in many stage 5e deposits pollen shows that the second transgression occurred late in the interglaciation and stratigraphic studies show that it reached 14 m it therefore fits very well antarctic ice surge models of stage 5 sea level and climate the socastee adds to the evidence for one or more sea levels above 0 m late in stage 5

sea level records at 80 ka from tectonically stable platforms florida and bermuda studies from tectonically active coasts on new guinea and barbados have suggested that sea level at 80 ka was significantly lower than present whereas data from the atlantic and pacific coasts of north america indicate an 80 ka sea level close to that of the present we determined ages of corals from a shallow submerged reef off the florida keys and an emergent marine deposit on bermuda both localities are on tectonically stable platforms distant from plate boundaries uranium series ages show that corals at both localities grew during the 80 ka sea level highstand and geologic data show that sea level at that time was no lower than 7 9 m below present florida and may have been 1 2 m above present bermuda the ice volume discrepancy of the 80 ka sea level estimates is greater than the volume of the greenland or west antarctic ice sheets comparison of our ages with high latitude insolation values indicates that the sea level stand near the present at 80 ka could have been orbitally forced

effects of microstructure on water imbibition in sandstones using x ray computed tomography and neutron radiography capillary imbibition in variably saturated porous media is important in defining displacement processes and transport in the vadose zone and in low permeability barriers and reservoirs nonintrusive imaging in real time offers the potential to examine critical impacts of heterogeneity and surface properties on imbibition dynamics neutron radiography is applied as a powerful imaging tool to observe temporal changes in the spatial distribution of water in porous materials we analyze water imbibition in both homogeneous and heterogeneous low permeability sandstones dynamic observations of the advance of the imbibition front with time are compared with characterizations of microstructure via high resolution x ray computed tomography ct pore size distribution mercury intrusion porosimetry and permeability of the contrasting samples we use an automated method to detect the progress of wetting front with time and link this to square root of time progress these data are used to estimate the effect of microstructure on water sorptivity from a modified lucas washburn equation moreover a model is established to calculate the maximum capillary diameter by modifying the hagen poiseuille and young laplace equations based on fractal theory comparing the calculated maximum capillary diameter with the maximum pore diameter from high resolution ct shows congruence between the two independent methods for the homogeneous silty sandstone but less effectively for the heterogeneous sandstone finally we use these data to link observed response with the physical characteristics of the contrasting media homogeneous versus heterogeneous and to demonstrate the sensitivity of sorptivity expressly to tortuosity rather than porosity in low permeability sandstones

quaternary coastal lithofacies sequence development and stratigraphy in a passive margin setting north carolina and virginia usa lithofacies analysis is fundamental to unravelling the succession of depositional environments associated with sea level fluctuations these successions and their timing are often poorly understood this report defines lithofacies encountered within the north eastern north carolina and south eastern virginia quaternary section interprets their depositional environments presents a model for coastal depositional sequence development in a passive margin setting and uses this understanding to develop the stratigraphy and quaternary evolutionary history of the region data were obtained from numerous drill cores and outcrops chronology was based on age estimates acquired using optically stimulated luminescence amino acid racemization uranium series and radiocarbon dating techniques geomorphic patterns were identified and interpreted using light detection and ranging imagery since lithofacies occurrence distribution and stratigraphic patterns are different on interfluves than in palaeo valleys this study focused on interfluves to obtain a record of highstand sea level cycles with minimal alteration by fluvial processes during subsequent lowstands nine primary lithofacies and four diagenetic facies were identified in outcrops and cores the uppermost depositional sequence on interfluves exhibits an upward succession from shelly marine lithofacies to tidal estuarine lithofacies and is bounded below by a marine ravinement surface and above by the modern land surface older depositional sequences in the subsurface are typically bounded above and below by marine ravinement surfaces portions of seven depositional sequences were recognized and interpreted to represent deposition from late middle pleistocene to present erosional processes associated with each successive depositional sequence removed portions of older depositional sequences the stratigraphic record of the most recent sea level highstands marine isotope stage 5a and marine isotope stage 3 is best preserved glacio isostatic adjustment has influenced depositional patterns so that deposits associated with late quaternary sea level highstands marine isotope stages 5c 5a and 3 which did not reach as high as present sea level according to equatorial eustatic records are uplifted and emergent within the study area

amino acid racemization geochronology of reworked quaternary mollusks on u s atlantic coast beaches implications for chronostratigraphy taphonomy and coastal sediment transport approximately 200 shells primarily mercenaria from 21 beach sites between new jersey and florida have been analyzed for the extent of racemization epimerization of their fossilized amino acids the greatest concentration of sites is in north carolina in regions least affected by human modification of natural beach sediment transport processes these results can be used to estimate the frequency of age mixing of pleistocene shell material in holocene depositional environments selected shells have also been dated by 14c conventional and or ams to provide direct calibration of the amino acid epimerization ratios shell taphonomic characteristics particularly color can be qualitatively related to apparent ages data for shell fragmentation combined with amino acid age estimates provide insights into probable transport distances of reworked shells shells with apparent pleistocene ages have epimerization values equivalent to those seen in onshore exposures of pleistocene coastal units amino acid epimerization measurements are a comparatively rapid and inexpensive chronologic tool for use in taphonomic and sediment shell transport studies paired amino acid 14c analyses on single shells provide insights into geochemical alteration of shells and permit modelling of the residence time of shells on beaches greater numbers of analyses at each site are needed before statistically valid estimates of age mixing can be obtained but the apparent distribution of pleistocene shells on atlantic coast beaches appears to be related to the distribution of pleistocene units in the shoreface and inner shelf and the thickness of holocene sedimentary cover in specific areas these observations provide useful criteria for the evaluation of possible age mixing of shells collected at outcrops of pleistocene units in the coastal plain

oxygen carbon and u series isotopes of aragonites from vestfold hills antarctica clues to geochemical processes in subglacial environments aragonites occurring in situ on the gneissic bedrock at vestfold hills an ice free coastal antarctic oasis possess morphologic and petrographic characteristics typical of subglacial carbonate precipitates the sup 14 c chronology of the samples is invalidated by modern carbon contamination and a sup 14 c sup 12 c reservoir correction of unknown magnitude in contrast u and th isotope analyses suggest that the subglacial deposits can be treated as closed datable systems if allowance is made for the excess sup 230 th derived from the small and variable detrital silicate fraction coexisting with the aragonites the mean sup 230 th depositional age of 35 000 plus minus 2 000 yrs correlates with late isotope stage 3 of deep sea glacial chronology and represents the time when the vestfold hills were partially or completely buried under the advancing east antarctic ice sheet the survival of the aragonites following the ice sheet retreat during the holocene is attributed to the extreme arid climate of the area the aragonites are anomalously depleted in sup 18 o and slightly depleted in sup 13 c relative to smow and pdb standards respectively delta sup 18 o 15 7 plus minus 0 9 per thousand delta sup 13 c minus 3 6 plus minus 0 4 per thousand the melt water with which the aragonitesmore would have equilibrated at 0 degree c is about 7 to 9 per thousand more depleted in sup 18 o relative to the extant basal ice source delta sup 18 o minus 41 per thousand part of this enhanced sup 18 o deficiency i e 4 to 6 per thousand is ascribed to temporal shifts in delta sup 18 o of the antarctic ice the rest to isotope effects of the subglacial hydrology a model of subglacial aragonite precipitation is proposed on the basis of water flow between warm melting zones and cold freezing zones at the ice sheet sole less

predicted bounds on peak global mean sea level during marine isotope stages 5a and 5c abstract estimates of marine isotope stage mis 5c and 5a global mean sea level gmsl based on marine terraces and coastal indicators range from 15 37 m and 9 30 m below present respectively tectonic displacement and glacial isostatic adjustment gia complicate efforts to refine this range we revisit this issue using numerical predictions of post glacial sea level change and updated estimates of site specific tectonic signals based upon these predictions laurentide and cordilleran peripheral bulge dynamics and variations in the gravitational effect of these ice masses dominate the gia signal along the east and west coasts of north america published compilations suggest that mis 5 sea level indicators extending from virginia to the caribbean lie on the outer flank of the peripheral bulge while those along a transect from oregon to baja california sit on the inner flank of the bulge our gia modeling reconciles these data by adopting a significantly weaker i e lower viscosity upper mantle in analyzing data on the pacific coast relative to the atlantic an inference supported by seismic tomography we present a sensitivity analysis that compares the observed elevation of globally distributed high stand markers to a suite of gia simulations that vary the earth model and gmsl from the last interglaciation mis 5e 130 115 ka to 70 ka we conclude that gmsl peaked at 8 5 4 6 m 1 during mis 5a and 9 4 5 3 m during mis 5c a more restrictive analysis yields slightly wider bounds corresponding to 10 5 5 5 m and 11 1 6 6 m respectively

late quaternary uplift rates of marine terraces on the pacific coast of north america southern oregon to baja california sur abstract marine terraces are common landforms along the pacific coast of north america from southern oregon to southern baja california we report 60 new uranium series ages of marine terrace corals hydrocorals and other fossils terraces representing the ca 80 ka and ca 125 ka high stands of sea are the most common along the pacific coast and we have used these ages along with terrace shoreline angle elevations and paleo sea level estimates to calculate late quaternary uplift rates uplift rates in the forearc region of the cascadia subduction zone range from 0 45 1 08 m kyr farther south along most of the coast west of the san andreas fault zone uplift rates range from 0 15 0 35 m kyr but some areas have significantly higher rates of uplift and others have apparently experienced little or no uplift in the last 125 ka in baja california sur west of the east pacific rise little or no uplift has occurred during the late quaternary on average the magnitude of rates of uplift for the tectonic regimes is as follows cascadia subduction zone san andreas fault zone region east pacific rise region

divergent evolution and the spatial structure of soil landscape variability abstract the spatial structure of soil variability at the landscape scale was examined on adjacent geomorphic surfaces dating from 80 to 200 ka in eastern north carolina the purpose was to determine whether there is evidence at broader scales distances of 102 104 m for the divergent evolution observed in the field at very detailed scales distances of 100 102 m the state probability function spf which measures spatial dependence for categorical environmental data along a transect was applied to soil series mapped at a 1 24 000 scale the older talbot terrace and younger pamlico terrace surfaces showed distinctly different patterns of spatial variability the range of spatial dependence was shorter on the older surface about 200 vs 300 m and the spf was higher at any given distance indicating more variability the spf for the pamlico surface also indicates a periodicity related to fluvial dissection of the landscape which is not readily detectable on the talbot transect despite its greater degree of dissection the results confirm earlier field studies which suggest that pedogenesis is marked by divergence whereby differences in initial conditions or local perturbations persist and increase to produce a more variable soil cover

permeability anisotropy and its relations with porous medium structure 1 the complete permeability tensor of 18 porous rock cores was determined by means of x ray tomography monitoring during the displacement of a salty tracer to study the effect of the pore space geometry on the anisotropy of permeability we compared the three dimensional shape of the invasion front with the x ray porosity maps obtained before injection the samples clean and shale bearing sandstones limestones and volcanic rocks belong to a broad variety of granulometry and pore space geometry their porosity ranges from 12 to 57 and their permeability ranges from 1 5 10 14 to 4 10 12 m2 for sandstones the permeability anisotropy is well correlated with the presence of bedding for volcanic rocks it is clearly related to the orientation of vesicles or cracks however for limestones no evident link between the geometry of the porous network and the permeability anisotropy appears probably because of the influence of the nonconnected porosity that does not contribute to the hydraulic transport this systematic work evidences the ability and the limitations of the tracer method to characterize the anisotropy of permeability in the laboratory in a simple and rapid way

late quaternary development of the croatan beach ridge complex bogue sound bogue banks nc usa and implications for coastal evolution abstract foraminiferal sedimentological geophysical and geochronologic data were utilized to elucidate the late quaternary geologic development of the croatan beach ridge complex cbrc bogue sound and bogue banks north carolina usa the cbrc is a relict beach ridge feature located on the mainland it is separated from the modern barrier island bogue banks by bogue sound seventeen cores along shore normal and shore parallel transects provided material for sedimentologic and foraminiferal analysis and resulted in the recognition of seven depositional facies representing a variety of coastal depositional environments chronologic and depositional facies data suggest the cbrc was initiated during mis 5a and rapid southward progradation produced a cape structure eolian reactivation of the upper sand of the cbrc occurred during the last glacial maximum 18 ka the age of flood tide delta deposits in bogue sound suggests that the holocene barrier island bogue banks had formed by 6 ka shoreface ravinement resulted in a shoreface landward of the present shoreline by 3 5 ka seaward and westward spit progradation of bogue banks began 1 7 ka and continued to 1 3 ka normal marine salinity conditions were present in bogue sound 1 1 ka suggesting removal of at least the narrowest parts of the barrier island coeval with a previously documented segmentation of the southern outer banks barrier islands previous work has linked this segmentation to climate warming and increased tropical storm activity during the medieval climate anomaly this study illustrates the complex response of this coastal system to pleistocene and holocene sea level and climate change over two major sea level cycles in particular the regional geomorphology during mis5a and the holocene sea level highstand differ significantly and this in large part was controlled by the antecedent geologic framework resulted in the contrasting more localized coastal geomorphic response

velocity analysis by iterative profile migration in conventional seismic processing velocity analysis is performed by using the normal moveout nmo equation which is based on the assumption of flat horizontal reflectors imaging by migration either before or after stack is done normally in a subsequent step using these velocities in this paper velocity analysis and imaging are combined in one step and migration itself is used as a velocity indicator because unlike nmo migration can be formulated for any velocity function migration based velocity analysis methods are capable of handling arbitrary structures i e those with lateral velocity variations in the proposed scheme each shot gather profile is migrated with an initial depth velocity model profile migration is implemented in the x domain but the actual implementation of profile migration is not critical as long as it is not done in a spatial wavenumber domain which would preclude handling of lateral velocity variations after migration with an initial velocity model the

reconciliation of sea level observations in the western north atlantic during the last glacial cycle abstract a south to north gradient of increasing marine isotope substage mis 5a 80 ka bp sea level has been recorded across the caribbean and surrounding region relative to present mis 5a sea levels range from 19 m to more than 3 m between barbados haiti the bahamas florida bermuda and the us atlantic coast in contrast no gradient in sea level is observed for the last interglacial period mis 5e 128 118 ka bp at tectonically stable localities in the same region with deposits generally lying several metres above present we demonstrate here that these controversial observations are reconciled by taking into account the isostatic response of the earth to glacial loading and unloading a fundamental effect that is commonly overlooked in the interpretation of sea level observations from different locations to define a global sea level curve furthermore the observed gradient can be used to place constraints on earth rheology and is an important indicator of the behaviour of the north american ice sheets during the last glacial cycle

investigation of coupling between surface processes and induced flow in the lower continental crust as a cause of intraplate seismicity many studies have highlighted the role of coupling between surface processes and flow in the lower continental crust in deforming the crust and creating topographic relief over quaternary timescales on the basis of the rheological knowledge gained it is suggested that intraplate seismicity can also be caused by coupling between surface processes and flow in the lower continental crust this view is shown to be a natural consequence of the modern idea that isostatic equilibrium is maintained by flow in the weak lower crust in response to erosion and sedimentation it is supported by a general correlation between the vigour of surface processes and rates of intraplate seismicity and by instances of seasonal seismicity that correlates with seasonal climate human interference in the environment can affect surface loading for instance deforestation for agriculture or urban development can cause increased erosion rates global warming is expected to cause increased storminess and thus increased erosion rates and or global sea level rise the possibility of increased rates of seismicity resulting from these processes should thus be considered in future hazard assessment copyright 2006 john wiley sons ltd

migration velocity analysis based on common shot depth migration applied to the seismic data of the caribbean oceanic plateau summary in areas where the geology is characterized by strong vertical and lateral velocity gradients pre stack depth migration will produce the optimum subsurface image an accurate velocity model is required for an accurate pre stack depth migration we developed a velocity analysis based on recursive pre stack depth migration that gives better results than the traditional cmp velocity analysis when applied to data over the caribbean oceanic plateau first the shot records are migrated with a series of constant velocities for each identified geological layer the velocity that best flattens the event in common receiver gathers crg is picked a large number of velocity analyses are run along the seismic line in order to define the reflector geometry for each layer we obtain the depth and interval velocity in order to make a model down to that depth this model is then used as the input for the next layer velocity analysis finally when all the layers have been picked the entire line is depth migrated with the derived model the migration algorithm used is a common shot kirchhoff technique which uses the ray tracing method of vidale 1988 to compute the traveltimes needed to determine the operator shape we applied this migration velocity analysis technique to seismic profiles of the casis cruise to define the deep structure of the caribbean oceanic plateau we imaged a 2500 m deep reflection sub b beneath the top of the plateau b horizon which defines the top of a 4500 4700 m s 1 layer the images obtained with this method will help to define odp sites that will provide information about geochemical and petrological variations of the volcanic basement

characterization of fluid flow in a shear band in porous rock using neutron radiography the challenge of understanding how localized deformation modifies fluid flow in porous rock is addressed new approaches are presented based on neutron radiography and digital image analyses to track fluid flow in rock specimens and to calculate flow velocity fields providing local flow measurements the results show that neutron radiography backed up by appropriate image analysis is a very powerful tool in this context being far more sensitive to the fluids in the rock than x ray radiography analysis of neutron radiography images of water imbibition into a laboratory deformed sandstone specimen has provided new measurements of local fluid flow velocities within a shear band indicating that flow is faster and water storage is higher in the band attributed to higher capillary forces associated with damage less

between beds and sequences stratigraphic organization at intermediate scales in the quaternary of the virginia coast usa stratigraphy presupposes a hierarchy of scales of spatial organization supplemented at the small scale end by sedimentological concepts beds bed sets and bed cosets and at larger spatial scales by sequence stratigraphic concepts systems tracts parasequences sequences between these two end members are intermediate sclae bodies described as lithofacies or simply facies a more restricted concept granulometric facies can be described in terms of horizontal grain size gradients facies change and cvclic vertical grain size gradients stratification assemblages of facies so defined also called depositional systems are not random loot occur in a limited suite of patterns such assemblages may be linked to two classes of bounding surfaces a source diastem the immediate source of the sediment and a surface of closure if preserved between which is sandwiched a transgressive or regressive basinward fining facies succession systems bounding surfaces are notably more continuous than internal gradational facies boundaries by thus restricting the definition of a facies assemblage depositional system it is possible to describe the quaternary of the virginia coast wish as few as 12 systems depositional systems in the quaternary of the virginia coast are allometric in that any system can be derived from any other by plastic expansion of one or more facies relative to another or by simple symmetry operations self similarity prevails across this intermediate scale of stratigraphic organization facies assemblages depositional systems consist of event beds which themselves have erosional basal boundaries and internal successions of microfacies at larger spatial so ales depositional systems are repeated either autocyclic repetitions forced by processes within the basin of deposition or allocyclic repetitions as parasequences and high frequency sequences in the virginia quaternary systems architecture is compatible with sequence architecture and nests conformably within its framework but analysis of systems architecture reveals rules beyond those governing sequence architecture

influence of open and sealed fractures on fluid flow and water saturation in sandstone cores using magnetic resonance imaging summary we use magnetic resonance imaging mri to image the imbibition of water by capillary action in a right cylindrical sample of a porous sedimentary rock with low iron content in the method some 55 repeat images are taken over a period of approximately two hours covering five vertical sections the evolution of the water flood front and the degree of water saturation can be observed by examining snapshots of proton density the results clearly show a the development of a rising wetting front in the rock matrix b preferential flow along open fractures observed on the core surface and c reduced flow associated with sealed fractures the inferred location orientation and connectivity of conducting and sealing fractures are confirmed by impregnating the sample after the test with an appropriate low viscosity setting resin and taking serial thin sections in destructive mode the results validate the utility of mri as a non destructive analytical tool for visualizing the distribution of water inside fractured porous media with low iron content the technique identifies paths of high and low permeability in the sample and quantifies the fracture location orientation and connectivity in sedimentary rocks preferential fluid flow in open fractures during capillary imbibition implies that the fractures are more water wet than the clasts within the matrix this may be due to due to differences in the age morphology and mineral structure on the surface of the pores and the fractures

geogenesis pedogenesis and multiple causality in the formation of texture contrast soils abstract coarse over fine vertical texture contrasts vtc are common in soils and weathering profiles in a variety of environmental settings including many where inheritance or surficial processes alone cannot account for them a multiple causality model is presented here which shows that texture contrasts can form in response to a combination of ubiquitous phenomena there are six key elements downward translocation by water erosional winnowing soil mixing by bioturbation the tendency for surface clay additions to be mobilized while subsurface clays are more likely to remain in place and biological facilitation of moisture flux no element alone is sufficient to create a vtc but not all are necessary in any given regolith the model is illustrated by application to case studies in the ouachita mountains arkansas ridgetops in eastern kentucky the lower coastal plain of north carolina and the upper coastal plain of east texas the implications for interpretation of soils paleosols and weathering profiles is that the presence of a textural contrast by itself does not connote any particular set of geogenic or pedogenic processs or controls texture contrasts may be geogenic pedogenic or both given the widespread occurrence of the mechanisms of the multiple causality model vertical texture contrasts are inevitable

amino acid geochronology of raised beaches in south west britain abstract based on 1 the epimerization of l isoleucine to d alloisoleucine d l ratios in patella vulgata littorina littorea l littoralis l saxatilis littorina species and nucella lapillus from raised beaches in south west britain 2 statistical analysis of the d l ratios and 3 lithostratigraphic and geomorphic evaluation three d l stages are proposed the d l ratios for all the species measured are converted to a patella vulgata standard the three d l stages are 1 1 the minchin hole d l stage d l ratios 0 175 0 014 defined at a stratotype in minchin hole cave gower wales 2 2 a provisionally defined but as yet unamed d l stage because of the current unavailability of a suitable stratotype with d l ratios of 0 135 0 014 3 3 the pennard d l stage d l ratios 0 105 0 016 defined at a stratotype in minchin hole cave gower wales two geochronological models of the three high sea level events representing the d l stages are constrained by uranium series age determinations on stalagmite interbedded with marine beds in minchin hole and bacon hole caves gower wales a potential fixed point in model evaluation is an age determination which is equivalent to oxygen isotope sub stage 5e 122 ka the two models are oxygen isotope stage and age ka bp d l stage d l ratio model 1a model 1b model 2 pennard 0 105 0 016 5a ca 80 5e 122 5e 122 5c ca 100 unnamed 0 135 0 014 5e 122 7 194 minchin hole 0 175 0 014 7 186 245 7 186 245 7 216 the ages of the raised beaches are used to constrain the timing and extent of glaciation in the area the extent of the late devensian glaciation is fixed by reference to localities where raised beaches of the pennard d l stage outcrop as well as by using unpublished data on molluscs incorporated into glacial deposits two pre devensian glaciations antedate the minchin hole d l stage the irish sea glaciation of the bristol channel irish sea older drift of south wales fremington till of north devon is ascribed to oxygen isotope 10 or earlier while the paviland welsh glaciation is ascribed to oxygen isotope stage 8 or earlier an earlier glaciation berwyn glaciation is inferred from erratics of known welsh provenance in essex

fast 4 d imaging of fluid flow in rock by high speed neutron tomography high speed neutron tomographies 1 min acquisition have been acquired during water invasion into air filled samples of both intact and deformed ex situ vosges sandstone three dimensional volume images have been processed to detect and track the evolution of the waterfront and to calculate full field measurement of its speed of advance the flow process correlates well with known rock properties and is especially sensitive to the distribution of the altered properties associated with observed localized deformation which is independently characterized by digital volume correlation of x ray tomographies acquired before and after the mechanical test the successful results presented herein open the possibility of in situ analysis of the local evolution of hydraulic properties of rocks due to mechanical deformation less

glacioisostatic influences on virginia s late pleistocene coastal plain deposits abstract the late pleistocene of virginia s outer coastal plain consists of sediments dated to marine isotope stages mis 5 and 3 two members from the tabb formation south of the chesapeake bay in southeastern virginia and two formations east of the bay on the southern delmarva peninsula were dated using optically stimulated luminescence osl the stratigraphically older butlers bluff member yielded osl ages of 70 ka 62 78 ka mis 5a and the younger poquoson member and wachapreague formation mis 3 ages of approximately 43 ka 33 50 ka and 42 ka 33 54 ka respectively these shoreface and near shore geologic units reached maximum altitudes ranging from 3 to 12 m above present sea level and were deposited when established glacial eustatic sea level curves suggest that sea levels were significantly lower than present by approximately 40 m if these new ages and the sea level curves are correct there must have been regional uplift of more than 40 m probably due to isostatic adjustments of forebulges peripheral to north american ice sheets when they were at their maxima during mis 6 and mis 2 if the late mis 6 forebulge collapse continued throughout mis 5 and mis 4 we propose that regional land elevations may have been low enough for deposition to occur during the lower eustatic sea levels of mis 3 during late mis 3 the units experienced renewed uplift followed by subsidence to present day elevations if this paraglacial region is not yet in isostatic equilibrium and still requires further forebulge subsidence this could explain the present day altitude and age discrepancies associated with these relict marine deposits

tau migration and velocity analysis theory and synthetic examples prestack migration velocity analysis in the time domain reduces the velocity depth ambiguity usually hampering the performance of prestack depth migration velocity analysis in prestack migration velocity analysis we keep the interval velocity model and the output images in vertical time this allows us to avoid placing reflectors at erroneous depths during the velocity analysis process and thus avoid slowing down its convergence to the true velocity model using a 1d velocity update scheme the prestack migration velocity analysis performed well on synthetic data from a model with a complex near surface velocity accurate velocity information and images were obtained using this time domain method problems occurred only in resolving a thin layer where the low resolution and fold of the synthetic data made it practically impossible to estimate velocity accurately in this layer this 1d approach also provided us reasonable results for synthetic data from the marmousi model despite the complexity of

age estimates and uplift rates for late pleistocene marine terraces southern oregon portion of the cascadia forearc marine terraces are prominent landforms along the southern oregon coast which forms part of the forearc region of the cascadia subduction zone interest in the cascadia subduction zone has increased because recent investigations have suggested that slip along plates at certain types of convergent margins is characteristically accompanied by large earthquakes in addition other investigations have suggested that convergent margins can be broadly classified by the magnitude of their uplift rates with these hypotheses in mind we generated new uranium series amino acid and stable isotope data for southern oregon marine terrace fossils these data along with terrace elevations and two alternative estimates of sea level at the time of terrace formation allow us to determine terrace ages and uplift rates uranium series analysis of fossil coral yields an age of 83 5 ka for the whisky run terrace at coquille point in bandon oregon a combination of amino acid and oxygen isotope data suggest ages of about 80 and 105 ka for the lowest two terraces at cape blanco these ages indicate uplift rates of 0 45 1 05 and 0 81 1 49 m kyr for coquille point and cape blanco respectively late quaternary uplift rates of marine terraces yield information about deformation in the overriding plate but it is unclear if such data vary systematically with convergent margin type in order to assess the utility of the southern oregon uplift rates for predicting the behavior of the cascadia subduction zone we compared late quaternary uplift rates derived from terrace data from subduction zones around the world on the basis of this comparison the southern oregon rates of vertical deformation are not unusually high or low furthermore late quaternary uplift rates show little relationship to the type of convergent margin these observations suggest that local structures may play a large role in uplift rate variability in addition while the type of convergent margin may place an upper limit on possible uplift rate greater upper limits serve to increase the range of possible uplift rates in the case of the southern oregon coast variability in uplift rate probably reflects local structures in the overriding plate and the rate of uplift cannot be used as a simple index of the potential for great earthquakes along the southern cascadia subduction zone

uranium concentration and isotope ratio profiles within mercenaria shells geochronological implications shells of nineteen specimens of mercenaria from unconsolidated sediments of the southeastern usa coast ranging in age from alive to pliocene were each separated into three to six sections parallel to the shell surface the uranium concentration and isotope ratio of each subsample was determined the results confirm those of previous studies that whole fossil shells have about 8 times as much uranium 300 vs 40 ppb and considerably higher 234u 238u ratios than do whole live collected shells however it was also found that uranium concentrations fall very steeply by factors of 300 and 15 in live and fossil shells respectively from the exterior of the shell to about two thirds of the shell thickness between this depth and the interior surface the uranium concentrations of live shells increase by about a factor of 5 while fossils have gradients which vary from moderately positive to moderately negative the most surprising finding of the study is that the interior portions of the shells become closed chemical systems by no more than about 15 ka after their death this is known from the observation that these portions of late pleistocene shells still have oceanic uranium isotope ratios while the exterior portions of the same shells have ratios which reflect an uptake of uranium from continental groundwaters the water the shells have been in contact with for the vast majority of their existence thus the u series ages of the interior portions of mercenaria shells may be valid after a small correction though shells older than about 200 ka seem less promising firm conclusions cannot be drawn regarding them because of the great scatter in the data

applications of x ray computed tomography in the geosciences x ray computed tomography ct is a technique that allows non destructive imaging and quantification of internal features of objects it was originally developed as a medical imaging technique but it is now also becoming widely used for the study of materials in engineering and the geosciences x ray ct reveals differences in density and atomic composition and can therefore be used for the study of porosity the relative distribution of contrasting solid phases and the penetration of injected solutions as a non destructive technique it is ideally suited for monitoring of processes such as the movement of solutions and the behaviour of materials under compression because large numbers of parallel two dimensional cross sections can be obtained three dimensional representations of selected features can be created in this book various applications of x ray ct in the geosciences are illustrated by papers covering a wide range of disciplines including petrology soil science petroleum geology geomechanics and sedimentology

quaternary facies assemblages and their bounding surfaces chesapeake bay mouth an approach to mesoscale stratigraphic analysis abstract shallow marine facies assemblages in the late quaternary section of virginia s eastern shore peninsula shed new light on the relationship between mesoscale stratigraphic units facies assemblages or depositional systems and the bounding surfaces from which they have been formed these units were deposited by the coast parallel progradation of the pleistocene barrier spit eastern shore peninsula during successive highstands as a consequence each segment of the spit complex has been produced by the coast parallel translation of a relatively small growth area at the spit tip the distal end of the present holocene barrier system appears to closely resemble the pleistocene highstand growth area and this environment consequently serves as a partial analog for interpreting the depositional environment of the fossil highstand deposits the many facies patterns present in the spit complex can be reduced to four kinds of facies assemblages depositional systems adopting a process based model facies template in this scheme definitions of both facies and facies assemblage are more limited than is the case in most textbook definitions in that the facies of a given assemblage are systematically related to each other by grain size and stratal pattern and also related to a bounding surface source diastem which is the immediate source of sediment for the facies assemblage vertical transitions between individual facies are easily identified in outcrop but the horizontal gradients of facies change are too gentle to be observed over the short dimensions of the borrow pits and do not have sufficient acoustic contrast to appear on ground penetrating radar records however the facies assemblages both in the borrow pits and on radar records stand out by virtue of their sharply defined bounding surfaces source diastems the facies assemblage either buries its source diastem or is capped by it the assemblages in the spit complex are in ascending stratigraphic order 1 several tidal shoal assemblages each underlain by a channel base diastem 2 two shoreface assemblages separated by an intervening marginal shoal assemblage and its underlying channel base diastem and 3 a beach strandplain assemblage underlain by a surf diastem all of these systems prograded southward as the nose of the spit prograded and while they did so zones of erosion cut the bounding surfaces that separate them two important bounding surfaces are conjugate surfaces that nourished both the facies assemblage above and the assemblage beneath as each surface advanced erosion at their leading edge spilled sediment forward down the nose of the spit while sediment was also swept backward aiding in the burial of the surface a conjugate surface creates a sandwich structure in which two facies assemblages are separated by the generating surface proximal facies are back to back across these sediment spreading boundaries episodic progradation of the spit tip by development of successive recurved beach ridges has overprinted the horizontal first order reflectors separating facies assemblages with gently dipping second order reflectors that separate successive growth increments of the spit although less clearly defined these growth increments are essentially high frequency autocyclic sequences and constitute the next higher scale of spatial organization above the depositional systems scale the manner in which facies have been organized into depositional systems in the late pleistocene highstand deposits of the eastern shore is specific to this estuary mouth setting these assemblages are however local expressions of a facies template that can be generalized to many other settings

transgressive systems tract development and incised valley fills within a quaternary estuary shelf system virginia inner shelf usa abstract high frequency quaternary glacioeustasy resulted in the incision of six moderate to high relief fluvial erosion surfaces beneath the virginia inner shelf and coastal zone along the updip edges of the atlantic continental margin fluvial valleys up to 5 km wide with up to 37 m of relief and thalweg depths of up to 72 m below modern mean sea level cut through underlying pleistocene and mio pliocene strata in response to drops in baselevel on the order of 100 m fluvially incised valleys were significantly modified during subsequent marine transgressions as fluvial drainage basins evolved into estuarine embayments ancestral generations of the chesapeake bay complex incised valley fill successions are bounded by or contain up to four stacked erosional surfaces basal fluvial erosion surface bay ravinement tidal ravinement and ebb flood channel base diastem in vertical succession these surfaces combined with the transgressive oceanic ravinement that generally caps incised valley fills control the lateral and vertical development of intervening seismic facies depositional systems transgressive stratigraphy characterizes the quaternary section beneath the virginia inner shelf where six depositional sequences sequences i vi are identified depositional sequences consist primarily of estuarine depositional systems subjacent to the transgressive oceanic ravinement and shoreface shelf depositional systems highstand systems tract coastal systems are thinly developed the quaternary section can be broadly subdivided into two parts the upper part contains sequences consisting predominantly of inner shelf facies whereas sequences in the lower part of the section consist predominantly of estuarine facies three styles of sequence preservation are identified style 1 represented by sequences vi and v is characterized by large estuarine systems ancestral generations of the chesapeake bay that are up to 40 m thick have hemicylindrical wedge geometries and occur within large coast oblique trending depressions paleo estuaries style 1 is dominated by fluvial through estuary mouth depositional systems seismic facies 1 4 style 2 sequence preservation represented by sequences iii and ii is dominantly an inner shelf and shoreface succession with a seaward thickening tabular wedge geometry that does not exceed 15 m in thickness these shoreface and inner shelf depositional systems of the upper transgressive systems tract seismic facies 9 and highstand systems tract seismic facies 7 and 11 are not associated with paleo estuaries style 3 sequence preservation is represented by sequence i the holocene sequence it consists of lower transgressive systems tract fluvial estuarine lagoonal and tidal inlet fill deposits seismic facies 1 6 and 8 overlain by upper transgressive systems tract shelf and shoreface sands seismic facies 9 style 3 has a crenulated wedge geometry and is thickest beneath and seaward of the modern chesapeake bay mouth it thins northward and landward onto late pleistocene interfluvial highs on the basinward side of the southern delmarva peninsula

an analysis and comparison of observed pleistocene south carolina usa shoreline elevations with predicted elevations derived from marine oxygen isotope stages geological maps of south carolina covering 6800 km2 confirm the existence of eight preserved pleistocene shorelines above current sea level marietta 42 6 m wicomico 27 4 m penholoway 21 3 m ladson 17 4 m ten mile hill 10 7 m pamlico 6 7 m princess anne 5 2 m and silver bluff 3 m current geochronologic data suggest that these eight shorelines correlate with marine oxygen isotope stages mis as follows marietta older than mis 77 wicomico mis 55 45 penholoway mis 19 or 17 ladson mis 11 ten mile hill mis 7 pamlico mis 5 princess anne mis 5 and silver bluff mis 5 or 3 except for the mis 5e pamlico and possibly the mis 11 ladson the south carolina elevations are higher than predicted by isotope proxy based reconstructions the 4 m of total relief from the pamlico to the silver bluff shoreline in south carolina for which other reconstructions suggest an expected relief of 80 m illustrates the lack of match our results suggest that processes affecting either post depositional changes in shoreline elevations or the creation of proxy sea level estimates must be considered before using paleo sea level position on continental margins

geochronology of a rich early pleistocene vertebrate fauna leisey shell pit tampa bay florida abstract leisey shell pit on the southeastern edge of tampa bay has produced the largest early pleistocene vertebrate fauna in north america consisting of about 30 000 cataloged specimens the predominantly terrestrial and freshwater vertebrate fauna was transported into an estuarine environment during a regressive phase in an otherwise marine bay bottom sequence of sandy shell beds the biochronological age of the leisey shell pit local fauna is late sappan or late early irvingtonian based on the presence of such mammalian species as mammuthus meridionalis and smilodon gracilis the absence of any blancan holdovers and early records of lutra nothrotheriops palaeolama and a new small glyptodont magnetostratigraphy indicates that the entire pleistocene section at leisey is reversed and thus presumably accumulated in the post olduvai part of the matuyama magnetochron i e 1 66 myr or younger strontium isotope ratios 87 sr 86 sr sampled from aragonitic bivalve shells chione cancellata trend higher with increasing height in the section yielding a mean age estimate for the two major bone beds of 1 7 0 35 myr in combination these three geochronologic methods provide a high resolution approach toward age determination and delimit the age of leisey shell pit local fauna as between 1 66 and 1 4 myr

microscale characterization of rupture nucleation unravels precursors to faulting in rocks abstract precursory signals manifestations of microscale damage that precedes dynamic faulting are key to earthquake forecasting and risk mitigation detections of precursors have primarily relied on measurements performed using sensors installed at some distance away from the rupture area in both field and laboratory experiments direct observations of continuous microscale damage accumulated during fault nucleation and propagation are scarce using an x ray transparent triaxial deformation apparatus we show the first quantitative high resolution three dimensional 3d information about damage evolution of rocks undergoing brittle failure the dynamic microtomography images documented a spectrum of damage characteristics and different fault growth patterns the interplay between various deformation mechanisms can result in either a positive negative or constant net volume change consequently changes in rock density and acoustic wave velocities before faulting are expected to vary in different tectonics settings hence making failure forecasting intrinsically dependent on rock type at depth

a cool eastern pacific ocean at the close of the last interglacial complex abstract new high precision thermal ionization mass spectrometric tims u series ages of solitary corals balanophyllia elegans from several marine terrace localities along the california and southern oregon coasts date to the 80 000 yr bp high stand of sea correlative with marine isotope substage 5a late in the last interglacial complex ages of multiple corals from localities north of point ano nuevo central california and san nicolas island southern california suggest that this high sea stand could have lasted at least 8000 yr from 84 000 to 76 000 yr bp these ages overlap with those from marine deposits on tectonically stable bermuda and tectonically emergent barbados higher elevation terraces at two california localities in the palos verdes hills and on san nicolas island have corals with ages that range mostly from 121 000 to 116 000 yr bp correlative with marine isotope substage 5e these ages are similar to those reported for other terraces in southern california but are younger than some ages reported from hawaii barbados and the bahamas marine terrace faunas are excellent proxies for nearshore marine paleotemperatures during past high sea stands terraces on the palos verdes hills and san nicolas island dated to the 120 000 yr bp high sea stand have dominantly zoogeographically neutral species in exposed coastal localities indicating nearshore waters similar to those of today in contrast 80 000 yr bp exposed coastal localities typically have molluscan faunas characterized by numerous extralimital northern species and a lack of extralimital southern species these fossil assemblages are indicative of nearshore water temperatures that were cooler than modern temperatures at 80 000 yr bp waters at least as warm as today s at 120 000 yr bp and cooler than present at 80 000 yr bp are in excellent agreement with marine alkenone records and coastal vegetation records derived from pollen data from both southern and northern california decreased insolation or increased upwelling seem inadequate to explain the cool waters off the pacific coast from southern oregon to southern california at 80 000 yr bp we propose that a stronger california current or at least one with a greater component of subarctic waters may explain cooler than modern coastal waters during the 80 000 yr bp high sea stand

migration velocity analysis accounting for the effects of lateral velocity variations the most common migration velocity analysis algorithms iterative profile migration focusing analysis and stack power analysis are based on restrictive subsurface assumptions that may cause the methods to break down in the presence of lateral velocity variations typically the subsurface is assumed to have either a constant velocity or at most a depth variable velocity recent innovations include the use of traveltime inversion philosophy to invert migration measurements of the curvature as a function of offset exhibited by an event following migration traveltime inversion makes few assumptions regarding the subsurface but is a rather unstable process thus an important question is under what conditions do the traditional methods break down and make the use of traveltime inversion methods mandatory marrying the common migration analysis with tomography results in a set of equations that while useful for generating updates from migration measurements are too complex for answering the above qu

uranium series coral ages from the us atlantic coastal plain the 80 ka problem revisited abstract uranium series coral ages for emergent units from the passive continental margin us atlantic coastal plain acp suggest sea level above present levels at the end of marine oxygen isotope stage mis 5 contradicting age elevation relations based on marine isotopic or coral reef models of ice equivalent sea level we have reexamined this problem by obtaining high precision 230th 238u and 231pa 235u thermal ionization mass spectrometric ages for recently collected and carefully cleaned acp corals many in situ we recognize samples that show no evidence for diagenesis on the basis of uranium isotopic composition and age concordance combining new and earlier data among those ages close to or within the age range of mis 5 over 85 cluster between 65 and 85 ka bp of the corals that we have analyzed those that show the least evidence for diagenesis on the basis of uranium isotopic composition and age concordance have ages between 80 and 85 ka bp consistent with a mis 5a correlation the units from which these samples have been collected are all emergent and have elevations within 3 5 m of those few units where early stage 5 125 000 ka bp coral ages have been obtained the acp appears to record an unusual history of relative sea level throughout mis 5 a history that is also apparent in the dated coral record for bermuda we speculate that this history is related to the regional near to intermediate field effects of ancestral laurentide ice sheets on last interglacial shorelines of the western north atlantic

acoustic emission and velocities associated with the formation of compaction bands in sandstone received 31 may 2005 revised 2 may 2006 accepted 22 june 2006 published 7 october 2006 1 a series of laboratory experiments has been conducted in which three dimensional 3 d locations of acoustic emissions ae were recorded and used to analyze the development of compaction bands in bleurswiller sandstone which has a porosity of 25 results were obtained for saturated samples deformed under triaxial compression at three different confining pressures 60 80 and 100 mpa a pore pressure of 10 mpa and room temperature we recorded acoustic emissions compressional and shear wave velocities and porosity reduction under hydrostatic condition and under triaxial loading conditions at a constant axial strain rate our results show that seismic velocities and their amplitude increased during hydrostatic pressure build up and during initial axial loading during shear enhanced compaction axial and radial velocities decreased progressively indicating an increase of stress induced damage in the rock in experiments performed at confining pressures of 80 and 100 mpa during triaxial loading acoustic emissions were localized in clusters during progressive loading ae clusters grow horizontally perpendicular to the maximum principal stress direction indicating formation of compaction bands throughout the specimens microstructural analysis of deformed specimens confirmed a spatial correspondence of ae clusters and compaction bands for the experiment performed at a confining pressure of 60 mpa ae locations and microstructural observations show symmetric compaction bands inclined to the cylinder axis of the specimen in agreement with predictions from recent theoretical models

theoretical correlations and lateral discontinuities in the quaternary aminostratigraphic record of the u s atlantic coastal plain abstract aminostratigraphic correlations of emergent quaternary deposits along the u s atlantic coastal plain have employed independent radiometric data regional temperature history models and assumptions regarding the nature of the preserved late quaternary sea level record on this passive margin a substantial aminostratigraphic offset is required if regional aminozones are rigorously constrained by all available th u data new insights regarding the relation of this offset to subsurface stratigraphy in the cape fear region of southeastern north carolina can explain these conflicts as consequences of the highly incomplete post cretaceous depositional record of the region southward projection of theoretical aminostratigraphic correlation trends suggests that stage 5 correlative marine units are rarely preserved on the emergent portion of the coastal plain between cape lookout and central south carolina and that samples of this age would be most frequently found in this region only as fragmentary and or reworked deposits on the inner shelf or in the subsurface of modern barrier islands if this hypothesis is correct then the accuracy of several th u coral dates from the south carolina coastal plain must be questioned along with sea level tectonic and paleoclimatic conclusions derived from these dates

uranium series age estimates and paleoclimatic significance of pleistocene tufas from the lahontan basin california and nevada abstract an extended chronology of lahontan basin lake levels based on uranium series age estimates correlates with the global ice volume record lake highstands occur at or shortly after times of maximum ice sheet size moderate size lakes occur when the global ice volume is about 80 of its maximum the data indicate that lake levels rise and fall relative to the proximity of the mean position of the jetstream when the continental ice sheet is above some threshold size or shape it appears that the large scale circulation and climatic conditions are right for producing lakes of moderate to large size within the lahontan basin

uranium series dating of fossil corals from marine sediments of southeastern united states atlantic coastal plain extensive low lying marine deposits border the southeastern united states atlantic coastal plain some units are fossiliferous and contain corals as isolated fragments in sediments of a detrital character these corals are subject to alteration processes such that suites of related samples must be examined to determine the suitability of these coral samples for reliable uranium series dating with the exception of those from one location most samples appear to have remained closed systems with respect to the isotopes of uranium and thorium throughout their geologic history extraneous 230th has been detected in some of the corals due to incorporation of some detrital materials into their skeletons for these samples different methods are applied to correct for the initial 230th contamination continued sampling and analyses have resulted in 55 individual uranium thorium determinations the average 230th ages of samples from the norfolk formation and from later and earlier deposited sediments of the wando formation are 71 000 87 000 and 129 000 yr and they appear to correlate with oxygen isotope substages 5a 5c and 5e respectively the average 230th age of samples from beds of the rappahannock river ponzer and ten mile hill localities is 212 000 yr and they correlate with oxygen isotope stage 7 the sediment of the canepatch formation is 460 000 yr old and it is tentatively correlated with oxygen isotope stage 11 there is general agreement between uranium series and uranium trend dates and between the quantitative trends of the amino acid data and uranium series dates the amino acid values however ure unacceptably high in at least two groups of samples those from localities near charleston south carolina and from central virginia

influence of mechanical damage on fluid flow patterns investigated using ct scanning imaging and acoustic emissions techniques 1 in order to get some insight into the influence of mechanical deformation on fluid flow patterns we performed series of x ray ct scanning runs during capillary imbibition experiments to image the water front displacement in bentheim sandstone samples a three steps procedure was followed 1 intact rock samples were tested 2 the samples were deformed in creep experiments under triaxial conditions with recording of acoustic emissions 3 the deformed samples experienced a second capillary imbibition test with ct scanning imaging using image analysis tools relevant flow parameters like the height velocity and curvature of the water front were measured stress induced damage had a significant impact on the flow patterns however contrasted results were obtained localized damage evidenced by acoustic emissions clustering resulted in one experiment in local disturbance of the flow patterns whereas in the second one a fracture detected by ct scan did not modify the local flow geometry

seismic reflection identification of susquehanna river paleochannels on the mid atlantic coastal plain abstract land based high resolution seismic reflection methods were used to image quaternary paleochannels of the susquehanna river system using a portable 12 channel signal enhancing seismograph 12 accelerometers as receivers and a 4 54 kg sledge hammer struck against an aluminum plate as a source a sixfold multichannel seismic profile 2 5 km long was acquired at taylors island maryland on the processed seismic profile pronounced high amplitude seismic reflections delineate the unconformity between quaternary and underlying tertiary sediments and the disconformable contact separating miocene and eocene deposits subsurface seismic stratigraphic relationships that clearly indicate the presence of two paleochannels were observed one believed to be the exmore paleochannel projected to underlie northern taylors island based on marine seismic data an overlapping sequence of fill sediments was observed on the eastern margin of the exmore paleochannel the second paleochannel may be a tributary of the exmore or possibly the western edge of the younger eastville paleochannel results from this study indicate that land based shallow high resolution seismic reflection data can be used to delineate subsurface geomorphology successfully in coastal plain environments this technique of defining erosional surfaces and depositional units beneath present land areas when integrated with chronostratigraphic data is a powerful tool for developing a better understanding of the quaternary record

ecological and paleoenvironmental information using stable isotope profiles from living and fossil molluscs stable oxygen and carbon isotopic profiles from recent specimens of spisula solidissima and placopecten magellanicus collected off the virginia coast are used to calibrate annual temperature controlled cycles in the 18o profile and shell growth characteristics the amplitude of the annual 18o cycles decreases with increasing water depth and may be used as a relative depth indicator the isotopic of profiles of two fossil specimens of pleistocene spisula are very similar in amplitude and character to modern analogues and verify the formation of annual growth increments in these fossil specimens offsets between the 18o profiles of the fossil and modern specimens are related to known temperature and ice volume effects during the late pleistocene and support the utility of mollusc isotope records as a stratigraphic tool carbon isotopic profiles from all specimens show light values in the spring and or fall associated with seasonal phytoplankton productivity offsets in the carbon isotopic composition between infaunal and epifaunal species may be related to sediment porewater geochemistry and oxidation of organic matter trends toward lighter 13c values through ontogeny suggest the effects of metabolic changes from a fast growing juvenile into a slower growing sexually mature adult anomalies in both the oxygen and carbon isotopic profiles identify the formation of minor shell growth increments as corresponding to hydrographic perturbations and to winter cold temperatures

the last interglacial period on the pacific coast of north america timing and paleoclimate new high precision u series ages of solitary corals balanophyllia elegans coupled with molluscan faunal data from marine terraces on the pacific coast of north america yield information about the timing and warmth of the last interglacial sea level highstand balanophyllia elegans takes up u in isotopic equilibrium with seawater during growth and shortly after death corals from the second terrace on san clemente island offshore southern california the third terrace on punta banda on the pacific coast of northern baja california and the discovery point formation on isla de guadalupe in the pacific ocean offshore baja california date to the peak of the last interglacial period and have u series ages ranging from ca 123 to 114 ka the first terrace on punta banda has corals with ages ranging from ca 83 to 80 ka which corresponds to a sea level highstand formed in the late last interglacial period u series analyses of corals from the cayucos terrace central california and the nestor terrace at point loma southern california show that these fossils have evidence of open system history similar to what has been reported by other workers for the same localities nevertheless a model of continuous secondary u and th uptake shows that two ages of corals are likely present at these localities representing the ca 105 and ca 120 ka sea level highstands reported elsewhere u series ages of last interglacial corals from the pacific coast overlap with but are on average younger than the ages of corals from barbados the bahamas and hawaii this age difference is explained by the nature of the geomorphic response to sea level change fringing or barrier reefs on low latitude coastlines have an accretionary growth style that keeps pace with rising sea level whether on a tectonically rising or stable coastline in contrast midlatitude high energy coastlines are sites of platform cutting during the early part of a sea level high stand and terrace scouring and concomitant sediment and fossil deposition as sea level starts to recede the youngest ages of corals from the pacific coast suggest that sea level was still relatively high at ca 116 ka which is not in agreement with other estimates of relatively large global ice volume at that time reliably dated ca 120 ka marine terrace deposits on the pacific coast have fossil mollusks that indicate water temperatures as warm or warmer than at present in contrast ca 80 ka marine deposits reported here and elsewhere have fossil mollusks indicating cooler than modern water temperatures the presence of both ca 105 ka and ca 120 ka corals on the nestor and cayucos terraces explains a previously enigmatic mixture of warm water and cool water mollusks at ca 105 ka a relatively high sea level with cool waters may have captured the terrace formed during the 120 ka sea level highstand in areas of low uplift rate the inference of cooler than modern waters off the pacific coast of north america at ca 80 ka and ca 105 ka based on marine terrace faunas does not agree with estimates of sea surface temperatures derived from alkenone studies in the santa barbara basin however cooler water temperatures at these times are in agreement with paleotemperature estimates from planktonic foraminiferal data for the santa barbara basin all records from central california to baja california whether from marine terraces or offshore cores indicate at least seasonably warmer than modern waters during the peak of the last interglacial period at ca 120 ka

uranium series dating of quaternary deposits abstract this is a review of u series dating methods as applicable to terrestrial sedimentary materials alpha counting techniques allow the dating of carbonates and phosphates with a precision of 5 to 10 over the time range from 1 ka to 350 ka atom counting methods mass spectrometry and ams substantially increase precision and may increase the range problems of contamination and open system behavior are discussed correction for detrital contaminant is demonstrated in the dating of speleothem from a cave in italy

quaternary depositional patterns and sea level fluctuations northeastern north carolina abstract a detailed record of late quaternary sea level oscillations is preserved within the upper 45 m of deposits along an eight km transect across croatan sound a drowned tributary of the roanoke albemarle drainage system northeastern north carolina drill hole and seismic data reveal nine relatively complete sequences filling an antecedent valley comprised of discontinuous middle and early pleistocene deposits on interfluves lithologically similar marine deposits of different sequences occur stacked in vertical succession and separated by ravinement surfaces within the paleo drainage marine deposits are separated by fluvial and or estuarine sediments deposited during periods of lowered sea level foraminiferal and molluscan fossil assemblages indicate that marine facies were deposited in a shallow marine embayment with open connection to shelf waters each sequence modifies or truncates portions of the preceding sequence or sequences sequence boundaries are the product of a combination of fluvial estuarine and marine erosional processes stratigraphic and age analyses constrain the ages of sequences to late marine isotope stage mis 6 and younger 140 ka to present indicating multiple sea level oscillations during this interval elevations of highstand deposits associated with late mis 5 and mis 3 imply that sea level was either similar to present during those times or that the region may have been influenced by glacio isostatic uplift and subsidence

a solution to anomalous fading and age shortfalls in optical dating of feldspar minerals abstract recent reports of age underestimations for events of interest in both palaeoclimatology and archaeology have led to questioning the validity of using luminescence for dating sediments the commonly designated culprit is anomalous fading of feldspar luminescence we investigated the differential fading rates of single feldspar grains in sediment samples from different geological domains of north america and deduced how one could extrapolate to zero fading this is shown to resolve an extreme case of optical age underestimation documented for the late pleistocene norfolk formation a key palaeoclimate stratigraphic unit exposed along the north american atlantic coast

development of texture contrast soils by a combination of bioturbation and translocation abstract soils and weathering profiles in a wide variety of parent materials and environmental settings exhibit coarse over fine vertical textural contrasts where these cannot be attributed to inherited texture contrasts or erosion deposition the most common explanations are based on translocation eluviation illuviation which removes clays from surface layers and deposits them in the subsoil or bioturbation where preferentially fine material is delivered to the surface by organisms from whence erosional winnowing creates a coarse surface layer in some soils of the lower coastal plain of north carolina u s a neither explanation is sufficient to explain the observed texture contrasts a heuristic model based on a combination of translocation of fine material from surface to subsoil and bioturbation driven delivery and recycling of material to the surface can explain the observed vertical textural contrasts the key elements in the model are coastal plain sediments which include some fine material eluviation illuviation by percolating water delivery of additional fine and mixed grain size material to surface by bioturbation making it available for translocation concentration of fine material originally scattered throughout the parent material in a b horizon and maintenance of vertical moisture fluxes by bioturbation the model is supported by morphological evidence of the key mechanisms argillic horizons that are finer than both the surface layers and underlying parent material evidence that argillic horizon formation is not limited by the rate of clay synthesis and the absence of texture contrasts in nearby soils formed from dune sands which lack fines

the record of major quaternary sea level changes in a large coastal plain estuary chesapeake bay eastern united states abstract seismic reflection surveys of the chesapeake bay combined with geologic mapping and analysis of boreholes on the delmarva peninsula provide evidence of at least three generations of the susquehanna river system and three generations of the chesapeake bay the evidence for ancient courses of the susquehanna river is preserved as three distinct paleochannels and evidence for ancient versions of the chesapeake bay is preserved as three sets of paleochannel fill beneath the bay and three generations of barrier spit deposits on the southern delmarva peninsula the paleochannels represent relative sea level minima and the channel fill and barrier spit deposits represents relative sea level maxima a history of three major marine transgressions is recorded in the stratigraphy preserved in the filled paleochannels and in the overlying barrier spit complexes three systematic progressions from fluvial to estuarine to bay or nearshore marine environments this sea level record seems to be compatible with the saw toothed pattern of the marine oxygen isotope record and with the concept of glacial interglacial terminations it also seems to have a climax character in which most of the preserved evidence is related to the largest terminations and to the extreme sea level positions that bound those terminations the three paleochannel fill and barrier spit complexes appear to correspond to oxygen isotope stages 1 5 and either 7 or 11 the three related paleochannels correspond to stages 2 6 and either 8 or 12

geochronologic evidence for a possible mis 11 emergent barrier beach ridge in southeastern georgia usa abstract predominantly clastic off lapping transgressive near shore marine sediment packages that are morphologically expressed as subparallel ne trending barriers beach ridges and associated back barrier areas characterize the near surface stratigraphic section between the savannah and the ogeechee rivers in effingham county southeastern georgia each barrier back barrier shoreline complex is lower than and cut into a higher older complex each barrier or shoreline complex overlies miocene strata no direct age data are available for these deposits previous researchers have disagreed on their age and provenance using luminescence and meteoric beryllium 10 10 be inventory analyses we estimated a minimum age for the largest westernmost morphologically identifiable and topographically highest barrier beach ridge the wicomico shoreline barrier and constrained the age of a suite of younger barrier beach ridges that lie adjacent and seaward of the wicomico shoreline barrier at the study site the near shore marine estuarine deposits underlying the wicomico shoreline barrier are overlain by eolian sand and an intervening zone of mixing optically stimulated luminescence osl data indicate ages of 43 ka for the eolian sand and 116 ka for the zone of mixing meteoric 10 be and pedostratigraphic data indicate minimum residence times of 33 4 ka for the eolian sand 80 6 ka for the zone of mixing and 247 ka for the paleosol the combined osl and 10 be age data indicate that at this locality the barrier beach ridge has a minimum age of about 360 ka this age for the wicomico shoreline barrier deposit is the first for any pleistocene near shore marine estuarine deposit in southeast georgia that is conclusively older than 80 ka the 360 ka minimum age is in agreement with other geochronologic data for near coastline deposits in georgia and south carolina the geomorphic position of this barrier beach ridge is similar to deposits in south carolina considered to be 450 ka to 1 ma the age and geomorphic data for georgia and south carolina possibly suggest the presence of mis 11 420 360 ka shoreline deposits between 15 m and 28 m above present sea level in the southeastern atlantic coastal plain

stetson pit dare county north carolina an integrated chronologic faunal and floral record of subsurface coastal quaternary sediments continuous split spoon samples from a drill hole penetrating 34 m of coastal plain sediments at stetson pit in dare county north carolina were taken for lithologic aminostratigraphic faunal ostracodes and floral pollen analyses three distinct aminozones are recognized in the subsurface section based upon d alloisoleucine l isoleucine a i values in each of the molluscan species mulinia lateralis and mercenaria sp ostracode zonations in the subsurface section are based on percentages of 80 thermophilic and cryophilic species those living today south and north of cape hatteras and the percentages of brackish water species five assemblage zones are delineated six pollen assemblage zones are also delineated within the subsurface section based upon study of 48 sediment samples the subsurface record at stetson pit is interpreted to represent portions of four interglacials based upon the combined faunal floral and aminostratigraphic data the two younger aminozones with amino acid age estimates of 100 000 20 000 yr 7 2 to 11 2 m msl and 300 000 500 000 yr 13 to 14 2 m msl represent portions of middle late pleistocene interglacials the lower aminozone 17 4 to 33 m msl spans an interval that probably includes at least two interglacials based upon faunal and floral records and has an age estimated to be between 800 000 and 1 300 000 yr boundaries delineated by faunal floral and amino acid methods do not always coincide due to sampling constraints and phase lags between the different records one major unconformity at 17 4 m msl in the stetson pit section is easily recognized from lithologic characteristics and may represent a hiatus of as much as 800 000 yr lithologic changes associated with all other zone boundaries are subtle and would probably not be considered significant in the absence of faunal floral or amino acid data

aminostratigraphic results from cape lookout n c and their relation to the preserved quaternary marine record of se north carolina abstract aminostratigraphic data were obtained for mulinia lateralis samples from closely spaced drillholes on the cape lookout north carolina barrier islands two major aminozones are recognized in the subsurface section based upon d alloisoleucine l isoleucine a i values these major aminozones can each be subdivided into two additional aminozones based upon direct comparisons with mulinia a i data from other north carolina localities correlation of the cape lookout mulinia aminostratigraphy with u series calibrated a i data in n c indicates that the sampled units represent deposition during the middle to late pleistocene the four cape lookout aminozones may be assigned to late and early stage 5 or possibly stages 5 and 7 a portion of the interval during stages 17 19 and at least one interglacial in stages 25 31 of the oxygen isotope record based on correlation to calibrated sites and kinetic model extrapolation the aminostratigraphic data obtained from the cape lookout barrier islands and nearby areas indicate that there are significant differences in the extent of preservation of the pleistocene sedimentary record to the southwest of cape lookout compared with that to the north northeast all four of the recognized cape lookout aminozones are present in the subsurface section to the north northeast of cape lookout in contrast the two late pleistocene aminozones are almost completely absent in the subsurface of the barrier islands and in onslow bay to the southwest of cape lookout these aminostratigraphic interpretations are consistent with the incomplete stratigraphic record recognized by previous investigators for the cape lookout onslow bay area the calibrated kinetic model age estimates for the cape lookout aminostratigraphic data now permit quantification of these stratigraphic gaps the detailed aminostratigraphic results from cape lookout also have significant consequences for regional aminostratigraphic correlations on the atlantic coastal plain and provide valuable information with which to test contrasting models proposed for regional correlation within the context of the preserved stratigraphic record

joint optimization of vertical component gravity and p wave first arrivals by simulated annealing abstractjoint seismic and gravity analyses of the san emidio geothermal field in the northwest basin and range province of nevada demonstrate that joint optimization changes interpretation outcomes the prior 0 3 0 5 km deep basin interpretation gives way to a deeper than 1 3 km basin model kirchoff prestack depth migrations reveal that joint optimization ameliorates shallow velocity artifacts flattening antiformal reflectors that could have been interpreted as folds furthermore joint optimization provides a clearer picture of the rangefront fault by increasing the depth of constrained velocities which improves reflector coherency at depth this technique provides new insight when applied to existing data sets and could replace the existing strategy of forward modeling to match gravity data we have achieved stable joint optimization through simulated annealing a global optimization algorithm that does not require an accurate initial model balancing the combined seismic gravity objective function i

quaternary stratigraphy and sea level history of the u s middle atlantic coastal plain abstract middle atlantic inner continental shelf stratigraphic studies document a regional late pleistocene fossiliferous mud deposit from northern new jersey to cape lookout north carolina seismic reconnaissance and detailed stratigraphic analyses reveal the nature of the mud termed unit q2 on the maryland inner continental shelf extensive amino acid relative age determinations from the single genus mulinia combined with additional amino acid analyses from onshore deposits having radiometric dates for calibration indicate an age range for unit q2 corresponding to oxygen isotope stage 5 ostracode assemblages delineate four distinct climatic episodes in unit q2 enabling correlation of the zones in q2 to the deep sea isotopic record of climatic fluctuations substages in stage 5 late stage 5 is represented on the maryland shelf by the 6 meter thick mud of unit q2 deposited in an open shelf environment at slightly depressed sea levels relative to substage 5e late stage 5 sea levels including sea level minima can be estimated for the mid atlantic coastal plain by direct measurement of the altitudes of ostracode zone boundaries offshore and from peak transgressive facies in correlative deposits onshore late stage 5 sea levels determined from the inner shelf and adjacent nearshore facies on the atlantic coast comprise the most complete sea level history for stage 5 yet proposed some recent revisions of glacioeustatic sea level models advocate slightly higher sea levels during late stage 5 substage 5c in particular than originally estimated from uplifting reef tracts and support sea levels higher than estimates from deep sea isotopic records the sea level record from the maryland inner continental shelf confirms these recent estimates in an area of minimal tectonism and adds sea level minima estimates for substages 5d and 5b offshore a more complete record of stage 5 is preserved than in onshore deposits which are limited to peak transgressive facies discrepancies in correlation among emerged coastal plain facies therefore become resolvable within the context provided by the shelf stratigraphy

applications of multiscale waveform inversion to marine data using a flooding technique and dynamic early arrival windows a recently developed time domain multiscale waveform tomography mwt method is applied to synthetic and field marine data although the mwt method was already applied to synthetic data the synthetic data application leads to a development of a hybrid method between waveform tomography and the salt flooding technique commonly use in subsalt imaging this hybrid method can overcome a convergence problem encountered by inversion with a traveltime velocity tomogram and successfully provides an accurate and highly resolved velocity tomogram for the 2d seg eage salt model in the application of mwt to the field data the inversion process is carried out using a multiscale method with a dynamic early arrival muting window to mitigate the local minima problem of waveform tomography and elastic effects with the modified mwt method reasonably accurate results as verified by comparison of migration images and common image gathers were obtained the hybrid method with the salt flooding technique is not used in this field data example because there is no salt in the subsurface according to our interpretation however we believe it is applicable to field data applications

timing and warmth of the last interglacial period new u series evidence from hawaii and bermuda and a new fossil compilation for north america abstract the timing and duration of the last interglacial period have been controversial with some studies suggesting a relatively short duration that is orbitally forced and others suggesting a long duration that is at most only partly related to orbital forcing new high precison thermal ionization mass spectrometric tims u series ages of last interglacial corals from hawaii and bermuda test these competing hypotheses waimanalo formation corals from slowly uplifting oahu hawaii range in age from 134 to 113 ka with most ages between 125 and 115 ka combined with published u series ages from nearby lanai the data suggest a long last interglacial period that may have occurred from 136 to at least 115 ka the results indicate that orbital forcing may not have been the only control on ice sheet growth and decay because sea level would have been high at times of relatively low northern hemisphere summer insolation on tectonically stable bermuda deposits from the 200 ka penultimate interglacial period 120 ka peak last interglacial period and 80 ka late last interglacial period high sea stands have been newly dated fossil corals on bermuda are derived from patch reefs that likely were catch up responses to sea level rise it is expected that u series ages of last interglacial corals on bermuda should overlap with but not be as old as the range of corals on oahu last interglacial corals on bermuda give a range of 125 113 ka which supports this hypothesis a large number of emergent marine deposits on hawaii bermuda and along coastal north america have now been dated to the last interglacial period both oahu and bermuda have marine invertebrate faunas with a number of extralimital southern species of mollusks suggesting warmer than present waters during the last interglacial period warmer waters are also suggested for last interglacial localities around most of north america from florida to canada and greenland and baja california to alaska these observations are consistent with similar warm water faunas of last interglacial age reported from japan the mediterranean basin and western australia it is likely that significant changes in ocean currents took place during the last interglacial period with a movement of relatively warm waters to higher latitudes than is the case today

the use of neutrons and monochromatic x rays for non destructive testing in geological materials in the paper we present our results for element sensitive high energy x ray tomography and high speed thermal neutron tomography applied to geological samples the tuneable monochromatic x ray beam was used for element sensitive tomography of geological samples containing heavy elements using the k edge dichromatic scanning technique this type of ndt non destructive testing allowed us to reveal the quantity and location of uranium lead and mercury in oklo samples natural nuclear reactor and cinnabar stones fast 3 d thermal neutron imaging of dynamical processes was successfully tested at the high flux neutron tomography station of the ill the qualitative investigation of water repellents and consolidants applied on sandstones of bray and limestones of maastricht were the first samples to be studied with the new imaging technique

morphometric analysis and amino acid geochronology of uplifted shorelines in a tectonic region near reggio calambria south italy the tectonic coastline of the calabrian peninsula provides an opportunity to study the morphology and history of elevated marine shorelines near capo dell armi eleven shorelines are preserved between sea level and 256 m with some correlation difficulties posed by the dissection of the area by intermittent streams we are able to correlate several of the shorelines across the entire study area with the support of correlations provided by amino acid geochronology we have identified four shorelines dating from the last interglacial period isotope stage 5 the oldest two both contain the strombus bubonius fauna and are of indistinguishable early last interglacial ages stage 5e aminozone e ca 125 ka the highest terrace vii is associated with a shoreline at 157 m and the lower with a shoreline around 125 105 m a s l of the two younger stage 5 without strombus bubonius the higher v lies at about 90 100 m and produces amino acid ratios slightly younger than but statistically indistinguishable from those of aminozone e however the youngest last interglacial shoreline deposits iv have produced amino acid ratios correlated to late stage 5 5a elsewhere in the mediterranean basin amino acid and geomorphic data have shown that uplift varies the study area from 0 85 to 1 03 m ka and suggeststhat constant uplift along any one traverse is unlikely