seismic detection of the lunar core despite recent insight regarding the history and current state of the moon from satellite sensing and analyses of limited apollo era seismic data deficiencies remain in our understanding of the deep lunar interior we reanalyzed apollo lunar seismograms using array processing methods to search for the presence of reflected and converted seismic energy from the core our results suggest the presence of a solid inner and fluid outer core overlain by a partially molten boundary layer the relative sizes of the inner and outer core suggest that the core is 60 liquid by volume based on phase diagrams of iron alloys and the presence of partial melt the core probably contains less than 6 weight of lighter alloying components which is consistent with a volatile depleted interior

genesis and evolution of a mid shelf storm built sand ridge new jersey continental shelf u s a abstract sand ridges form discrete parts of a modern surficial veneer on many continental shelves worldwide yet are seldom cited as analogs for isolated marine sand bodies found in outcrop or the subsurface one reason may be that a comprehensive explanation for the evolution of modern mid shelf sand ridges has proven elusive new information most notably high resolution seismic data collected on modern sand ridges in adjacent areas by other workers has led to this reevaluation of a largely unpublished but extensive vibracore dataset from a mid shelf sand ridge off new jersey usa the presence of dipping reflections within other ridges is particularly notable on new high resolution seismic data but has yet to be confirmed in these other ridges by extensive coring reexamining the original well preserved vibracore peels from the mid shelf sand ridge sampled in the 1980s reveals that these internal reflections could be associated with burrowed low density mud beds new cross sections constructed with 20 vibracores suggest that the dipping internal reflections are accretionary surfaces associated with episodic ridge migration to the east and south radiocarbon dating indicates that the mid shelf sand ridge has migrated episodically over the last 5 ka and movement probably continues today during major storms this documented migration continues well after transgressive ravinement approximately 9 10 ka contradicting existing views that mid shelf ridges become moribund sometime after detachment from the shoreline the morphology migration history and internal sedimentary character suggest that the ridges are acting much like primary bedforms although these sand bodies are much larger in scale 5 to 8 m height or thickness than typical subaqueous dunes observed on modern storm dominated shelves

three dimensional finite element modelling of earth s viscoelastic deformation effects of lateral variations in lithospheric thickness summary we have developed a 3 d spherical finite element model to study the dynamic response to surface loads of a self gravitating and incompressible earth with 3 d viscoelastic structure we have forced our model with the ice 3g deglaciation history of tushingham peltier to study the effects of laterally varying lithospheric thickness on observations of post glacial rebound pgr the laterally varying lithospheric thicknesses are derived from estimates of the thermal structure of the oceanic lithosphere and from elastic thicknesses on continents as estimated from studies of long term geological loads our calculations show that the effects of lithospheric structure on the relative sea level change rslc depend on the locations of the observation sites and on the size of loads the rslc at the centre of the north american ice sheet is significantly less sensitive to lithospheric thickness compared with the rslc at the centre of the fennoscandian ice sheet at the peripheral bulges the rslc tends to be more sensitive to lithospheric thickness the rslc is controlled by local lithospheric thickness the rslc at a given location as predicted using models with laterally varying lithospheric thickness can be reproduced using a 1 d model with a uniform lithospheric thickness equal to the local lithospheric thickness coupled with efficient parallel computing we believe that the finite element model that we present here can be used to address a variety of viscoelastic deformation problems in geodynamics

coupling of thermal evolution and despinning of early iapetus abstract the cassini mission revealed two spectacular characteristics of iapetus 1 a geologically old and high equatorial ridge which is unique in the solar system and 2 a large flattening of 35 km consistent with the equilibrium figure for a hydrostatic body rotating with a period of 16 h whereas the current spin period is 79 33 days this study describes three dimensional simulations of solid state convection within an undifferentiated iapetus it investigates the implications for the evolution of the interior thermal structure and its spin rate and global shape using radially layered viscoelastic models the role of the concentration in the short lived radiogenic element 26 al just after accretion is completed is specifically addressed the first result is to show that whatever the 26 al value convection occurs as suggested by castillo rogez et al castillo rogez j matson d sotin c johnson t lunine j thomas p 2007 icarus 190 179 202 convection reduces the warming of the interior compared to the conductive evolution and therefore limits the conditions for despinning in our calculations two conceptual linear viscoelastic models are used when considering a maxwell rheology the interior temperature viscosity never reaches a value high low enough to induce despinning in order to promote dissipation at low temperature a burgers rheology which includes an additional dissipation peak is introduced for favorable parameter values this latter rheology leads to despinning however only models associated with large amounts of short lived radiogenic elements 26 al 25 ppb lead to the observed flattening this suggests that the accretion process needs to be completed shortly after the formation of cais calcium aluminum rich inclusions 4 myr for 26 al varying between 72 and 46 ppb the observed flattening is obtained only for a limited range of initial spin period between 9 5 and 10 2 h for 26 al ranging between 30 and 15 ppb initial spin rates smaller than 8 5 h are required for smaller values of 26 al the body is too cold and viscous to acquire a significant flattening even if a rotation period close to the body disruption limit is considered even with a thin lithosphere during the early stage our simulations show that iapetus never reaches the equilibrium figure for a hydrostatic body due to the non zero rigidity of the lithosphere the 35 km value of the flattening is the result of the partial relaxation of an ancient larger flattening ranging between 45 and 80 km depending on the evolution of the lithosphere thickness mainly controlled by the radiogenic content a thin lithosphere is consistent with an early building of the equatorial ridge the lithosphere thickening due to interior cooling can explain the preservation of the ridge throughout the remaining evolution of iapetus

shallowly buried enigmatic seismic stratigraphy on the new jersey outer shelf evidence for latest pleistocene catastrophic erosion chirp seismic profiles reveal a prominent seismic facies boundary 0 20 m below the seafloor within an 8 6 10 2 km area of the new jersey outer shelf this irregular boundary separates seismically transparent facies from underlying stratified facies the irregularities form two populations of incisions trending northeast and east northeast stratified blocks within the transparent facies occasionally within presumed incisions together with lithologic evidence indicate that some of the transparent facies was formed by disruption of the stratified facies preservation of steep 50 90 incision flanks implies that deposition of the transparent facies closely followed disruption catastrophic erosion and redeposition following the multiple breaching of glacial lake dams to the north ca 19 12 ka constitute the likeliest mechanisms both for producing facies boundary incisions and emplacing the transparent facies implying that local forcing can generate erosional unconformities on periglacial shelves in the absence of base level change this facies boundary adds complexity to the already complex shallowly buried stratigraphic record of the last glacio eustatic cycle on the new jersey continental shelf long considered typical of periglacial shelves worldwide

recognition of 3850 ma water lain sediments in west greenland and their significance for the early archaean earth a layered body of amphibolite banded iron formation bif and ultramafic rocks from the island of akilia southern west greenland is cut by a quartz dioritic sheet from which shrimp zircon 206pb 207pb weighted mean ages of 3865 11 ma and 3840 8 ma 2 sigma can be calculated by different approaches three other methods of assessing the zircon data yield ages of 3830 ma the bifs are interpreted as water lain sediments which with a minimum age of approximately 3850 ma are the oldest sediments yet documented these rocks provide proof that by approximately 3850 ma 1 there was a hydrosphere supporting the chemical sedimentation of bif and that not all water was stored in hydrous minerals and 2 that conditions satisfying the stability of liquid water imply surface temperatures were similar to present carbon isotope data of graphitic microdomains in apatite from the akilia island bif are consistent with a bio organic origin mojzsis et al 1996 extending the record of life on earth to 3850 ma life and surface water by approximately 3850 ma provide constraints on either the energetics or termination of the late meteoritic bombardment event suggested from the lunar cratering record on earth

once again once again tidal friction topex poseidon t p altimetry has reopened the problem of how tidal dissipation is to be allocated there is now general agreement of a m2 dissipation by 2 5 terawatts 1 tw 1012 w based on four quite separate astronomic observational programs allowing for the bodily tide dissipation of 0 1 tw leaves 2 4 tw for ocean dissipation the traditional disposal sites since jeffreys 1920 have been in the turbulent bottom boundary layer bbl of marginal seas and the modern estimate of about 2 1 tw is in this tradition but the distribution among the shallow seas has changed radically from time to time independent estimates of energy flux into the marginal seas are not in good agreement with the bbl estimates t p altimetry has contributed to the tidal problem in two important ways the assimilation of global altimetry into laplace tidal solutions has led to accurate representations of the global tides as evidenced by the very close agreement between the astronomic measurements and the computed 2 4 tw working of the moon on the global ocean second the detection by ray and mitchum 1996 of small surface manifestation of internal tides radiating away from the hawaiian chain has led to global estimates of 0 2 to 0 4 tw of conversion of surface tides to internal tides measurements of ocean microstructure yields 0 2 tw of global dissipation by pelagic turbulence away from topography we propose that pelagic turbulence is maintained by topographic scattering of barotropic into baroclinic tidal energy via internal tides and internal waves previous estimates by baines 1974 baines 1982 of this conversion along 150 000 km of continental coastlines gave a negligible 0 02 tw evidently the important conversion takes place along mid ocean ridges the maintenance of the abyssal global stratification requires a much larger expenditure of power 2 tw versus 0 2 tw this is usually attributed to wind forcing if tidal power is to play a significant role here then the bbl estimates need to be reduced the challenge is to estimate dissipation from the energy flux divergence in the t p adjusted tidal models without prior assumptions concerning the dissipation processes

tracking the last sea level cycle seafloor morphology and shallow stratigraphy of the latest quaternary new jersey middle continental shelf seafloor geomorphology and surficial stratigraphy of the new jersey middle continental shelf provide a detailed record of sea level change during the last advance and retreat of the laurentide ice sheet 120 kyr b p to present a nw se oriented corridor on the middle shelf between water depths of 40 m the mid shelf paleo shore and 100 m the franklin paleo shore encompasses 500 line km of 2d huntec boomer profiles 500 3500 hz an embedded 4 6 km2 3d volume and a 490 km2 swath bathymetry map we use these data to develop a relative stratigraphy core samples from published studies also provide some chronological and sedimentological constraints on the upper 5 m of the stratigraphic succession the following stratigraphic units and surfaces occur from bottom to top 1 r a high amplitude reflection that separates sediment 46 5 kyr old by ams 14c dating from overlying sediment wedges 2 the outer shelf wedge a marine unit up to 50 m thick that onlaps r 3 channels a reflection sub parallel to the seafloor that incises r and appears as a dendritic system of channels in map view 4 channels fill the upper portion of which is sampled and known to represent deepening upward marine sediments 12 3 kyr in age 5 the t horizon a seismically discontinuous surface that caps channels fill 6 oblique ridge deposits coarse grained shelly units comprised of km scale shallow shelf bedforms and 7 ribbon floored swales bathymetric depressions parallel to modern shelf currents that truncate the oblique ridges and cut into surficial deposits we interpret this succession of features in light of a global eustatic sea level curve and the consequent migration of the coastline across the middle shelf during the last 120 kyr the morphology of the new jersey middle shelf shows a discrete sequence of stratigraphic elements and reflects the pulsed episodicity of the last sea level cycle r is a complicated marine non marine erosional surface formed during the last regression while the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum wisconsin lowstand i e marine oxygen isotope stage 3 1 channels is a widespread fluvial subarial erosion surface formed at the late wisconsin glacial maximum 22 kyr b p the shoreline migrated back across the mid shelf corridor non uniformly during the period represented by channels fill oblique ridges are relict features on the new jersey middle shelf while the ribbon floored swales represent modern shelf erosion there is no systematic relationship between modern seafloor morphology and the very shallowly buried stratigraphic succession

removal of diurnal tidal effects from an ultra high resolution 3 d marine seismic survey on the continental shelf offshore new jersey an ultra high resolution 3 d single channel seismic survey was performed off the coast of new jersey in 1993 to study the late quaternary history of sedimentation on the northwest atlantic continental margin see davies et al 1992 as a part of the office of naval research strataform initiative nittrouer and kravitz 1995 three different sets of profiles were acquired figure 1 but only the set with highest spatial density is discussed here a single ten element receiver recorded 300 ms of data for every shot during the survey which covers a total area of 0 6 km north south 7 75 km east west see table 1 the deep towed huntec source deployed at 30 m depth produced frequencies of 500 to 3500 hz a band pass filter with corner frequencies at 1000 and 3500 hz was applied during preprocessing

seismic and bathymetric evidence for four different episodes of iceberg scouring on the new jersey outer shelf possible correlation to heinrich events abstract re analysis of dense chirp seismic surveys on the outer new jersey shelf reveals two sets of shallowly buried incisions the incisions are linear to slightly sinuous oriented ne sw and exhibit cross cutting relationships we interpret both sets as paleo iceberg scours one set cuts into the r horizon a regional unconformity that formed 45 40 ka and which was subsequently buried by the finer grained outer shelf sediment wedge osw the second set is part of an erose boundary between a layered lower unit of the osw and an upper more transparent unit the erose boundary scours are deeper and have steeper slopes than the r horizon scours the latter often exhibit bermed edges whereas the former do not these differences in cross sectional morphology are likely determined by the material properties of the sediments being scoured sand at the r horizon and clay at the erose boundary the orientation of both sets of scours is consistent with previously recognized iceberg scours in stratigraphically younger seafloor on the outer new jersey shelf in 110 150 m water depths located 40 km to the northeast we argue that heinrich events recurring periods of massive iceberg flux into the north atlantic represent the most likely times for transporting icebergs to these latitudes based on stratigraphic relationships a recently published ambient sea level curve and radiocarbon age constraints we attribute the r horizon scours to heinrich event h4 37 cal ka the erose boundary scours to h3 30 cal ka and the seafloor scours to h2 23 cal ka and or h1 17 cal ka facies changes immediately following the r horizon and erose boundary scours may be related to heinrich event forced climate changes perhaps the onset of interstadial conditions and associated melt water pulses floods these pulses floods repeatedly carried fine grained rock flour produced by widespread glacial erosion to the new jersey shelf

high resolution 3d seismic reflection and coring techniques applied to late quaternary deposits on the new jersey shelf studies of variable small scale features typical of quaternary glacimarine environments require an interdisciplinary approach precisely navigated high resolution 3d seismic surveys nested within a regional 2d seismic framework and integrated with a precisely navigated coring program designed to sample specific shallow acoustic facies we illustrate this approach with examples from continuing studies of sediments on the new jersey continental shelf surficial stratigraphy associated with the latest pleistocene holocene deglaciation has been imaged twice in true 3d using the huntec dts system a deep towed high frequency 500 3500 hz boomer source in both cases nominal profile spacing was 10 m 2 5 m shot points penetration of 40 ms 30 m was achieved seismic facies in the upper 5 m have been interpreted using differential gps navigated vibra cores accuracy of position of both seismic profiles and core locations approaches 5 m much smaller than the wavelengths of the geologic features being imaged sampled survey results show multiple sediment filled channels buried beneath the modern outer shelf meandering south and southeast in the general direction of the shelf edge channels are typically a few meters deep and 100 200 m across lateral continuity between the channeled surfaces within the outer shelf wedge and the mid shelf cannot be demonstrated because of later erosion but both sets of channels incise reflector r believed to be a pre late wisconsinan exposure surface ams14c dates on benthic foraminifers from cores show that channels on the midshelf are cut into sediment 45 000 yrs old and filled with muddy sediment as young as 12 500 yrs whereas channels on the outer shelf are filled with coarser and perhaps older sediment both sets of filled channels are buried beneath a surficial sand layer the integrated approach described here can remove some uncertainties and considerably sharpen the quaternary stratigraphic picture without the perspective obtained from 3d seismic surveys and equally precise sampling interpretations based on broader regional seismic surveys and spot coring are inevitably constrained by the potential for mismatching shallow acoustic and sedimentary facies

effects of orbital evolution on lunar ice stability 1 many regions near the lunar poles are currently cold enough that surface water ice would be stable against sublimation losses for billions of years however most of these environments are currently too cold to efficiently drive ice downward by thermal diffusion leaving impact burial as the primary means of protection from surface loss processes in this respect most of the present near surface thermal environments on the moon may actually be quite poor traps for water ice this was not always the case long term orbital changes have dramatically altered the lunar polar thermal environment we develop a simple model of the evolution of the lunar orbit and spin axis to examine the thermal environments available for volatile deposition and retention in the past our calculations show that some early lunar polar environments were in the right temperature regime to have collected subsurface ice if a supply were available however a high obliquity period which occurred when the moon was at about half its present distance from the earth would either have driven this ice out into space or deep into the lunar subsurface since that time as the lunar obliquity has slowly decreased to its present value environments have undergone their own thermal evolution and each of the current cold traps experienced a period when they were most efficient at thermally burying ice we examine the thermal history of a lunar polar crater to provide a framework for examining other processes effecting volatiles in the moon s near surface cold traps

solid tidal friction above a liquid water reservoir as the origin of the south pole hotspot on enceladus abstract earth jupiter s moon io and saturn s tiny moon enceladus are the only solid objects in the solar system to be sufficiently geologically active for their internal heat to be detected by remote sensing interestingly the endogenic activity on enceladus is only located on a specific region at the south pole from which jets of water vapor and ice particles have been observed spencer j r and 9 colleagues 2006 science 311 1401 1405 porco c c and 24 colleagues 2006 science 311 1393 1401 the current polar location of the thermal anomaly can possibly be explained by diapir induced reorientation of the satellite nimmo f pappalardo r t 2006 nature 441 614 616 but the thermal anomaly triggering and the heat power required to sustain it over geological timescales remain problematic using a three dimensional viscoelastic numerical model simulating the response of enceladus to tidal forcing we explore the effect of a low viscosity anomaly in the ice shell localized to the south polar region on the tidal dissipation patterns we demonstrate that only interior models with a liquid water layer at depth can explain the observed magnitude of dissipation rate and its particular location at the south pole moreover we show that tidally induced heat must be generated over a relatively broad region in the southern hemisphere and it is then transferred toward the south pole where it is episodically released during relatively short resurfacing events as large tidal dissipation and internal melting cannot be induced in the south polar region in the absence of a pre existing liquid decoupling layer we propose that liquid water must have been present in the interior for a very long period of time and possibly since the satellite formation owing to the orbital equilibrium requirement meyer j wisdom j 2007 icarus 188 535 539 sustaining some liquid water at depth is impossible if heat is continuously emitted at a rate of 4 8 gw at the south pole based on that requirement we propose that the current thermal emission is not in equilibrium with the heat production and that the thermal emission rate is abnormally high at present time alternatively continuous dissipation at a rate of 1 2 gw in the ice shell at the south pole should be sufficient to induce internal melting and it could sustain a layer of liquid water at depth over geologic timescales

the tidal rotational shape of the moon and evidence for polar wander analysis of the moon s topography reveals that when its largest basins are removed the lunar shape is consistent with processes controlled by early earth tides and implies a reorientation of the moon s principal shape axes attempts to assess the various theories for the formation of the moon and to determine its true shape are complicated by the presence of several large basins on its surface that formed after the crust solidified here ian garrick bethell et al concentrate on the topography and gravity outside these basins and propose that the long wavelength shape of the moon has evolved through a combination of two early tidal processes first a crust building process controlled by early tidal heating throughout the moon and second the later development of a frozen tidal rotational bulge the authors also infer that an uneven distribution of internal density eventually reoriented the moon s polar axis by about 36 to the configuration that we see today the origin of the moon s large scale topography is important for understanding lunar geology1 lunar orbital evolution2 and the moon s orientation in the sky3 previous hypotheses for its origin have included late accretion events4 large impacts5 tidal effects6 and convection processes7 however testing these hypotheses and quantifying the moon s topography is complicated by the large basins that have formed since the crust crystallized here we estimate the large scale lunar topography and gravity spherical harmonics outside these basins and show that the bulk of the spherical harmonic degree 2 topography is consistent with a crust building process controlled by early tidal heating throughout the moon the remainder of the degree 2 topography is consistent with a frozen tidal rotational bulge that formed later at a semi major axis of about 32 earth radii the probability of the degree 2 shape having both tidal heating and frozen shape characteristics by chance is less than 1 we also infer that internal density contrasts eventually reoriented the moon s polar axis by 36 4 to the configuration we observe today together these results link the geology of the near and far sides and resolve long standing questions about the moon s large scale shape gravity and history of polar wander

storm enhanced plasma density and polar tongue of ionization development during the 15 may 2005 superstorm we investigate the ionosphere s global response to the 15 may 2005 superstorm in terms of storm evolution and ionospheric electrodynamics our aim is to study the global distribution of plasma and the resultant large scale ionospheric features including the equatorial ionization anomaly eia storm enhanced density sed and polar tongue of ionization toi we have combined multi instrument ionospheric data solar and terrestrial magnetic data and polar convection maps results reveal the prompt penetration of the interplanetary electric field to the polar region and then to the equator with a dusk to dawn polarity during the initial phase and with a dawn to dusk polarity during the main phase this drove during the initial phase a weak eastward equatorial electrojet eej in the american sector at nighttime and a weak westward eej in the indian australian sector at daytime during the main phase these eejs intensified and changed polarities sed and polar toi development was observed prior to and during the initial phase at evening premidnight hours over north america and during the main phase in the south at afternoon evening hours in the australian sector during the main phase and early in the recovery phase the eia sed structure was well formed in the asian longitude sector then polar toi development was absent in the north because of the long distance from the magnetic pole but was supported in the south because of the closeness of daytime cusp and magnetic pole thus the eia sed toi structure developed twice but each time in a different longitude sector and with different characteristics

geological constraints on the precambrian history of earth s rotation and the moon s orbit over the past decade the analysis of sedimentary cyclic rhythmites of tidal origin i e stacked thin beds or laminae usually of sandstone siltstone and mudstone that display periodic variations in thickness reflecting a strong tidal influence on sedimentation has provided information on earth s paleorotation and the evolving lunar orbit for precambrian time before 540 ma depositional environments of tidal rhythmites range from estuarine to tidal delta with a wave protected distal ebb tidal delta setting being particularly favorable for the deposition and preservation of long detailed rhythmite records the potential sediment load of nearshore tidal currents and the effectiveness of the tide as an agent of sediment entrainment and deposition are related directly to tidal range or maximum tidal height and consequent current speed hence the thickness of successive laminae deposited by tidal currents can be a proxy tidal record with paleotidal and paleorotational values being determined by analysis of measured records of lamina and cycle thickness the validity of the findings can be investigated by testing the primary observed values for internal self consistency through application of the laws of celestial mechanics paleotidal and paleorotational values provided by late neoproterozoic 620 ma tidal rhythmites in south australia are validated by these tests and indicate 13 1 0 1 synodic lunar months yr 400 7 solar days yr a length of day of 21 9 0 4 h and a relative earth moon distance a a0 of 0 965 0 005 the mean rate of lunar recession since that time is 2 17 0 31 cm yr which is little more than half the present rate of lunar recession of 3 82 0 07 cm yr obtained by lunar laser ranging the late neoproterozoic data militate against significant overall change in earth s moment of inertia and radius at least since 620 ma cyclicity displayed by paleoproterozoic 2450 ma banded iron formation in western australia may record tidal influences on the discharge and or dispersal of submarine hydrothermal plumes and suggests 14 5 0 5 synodic months yr and a a0 0 906 0 029 the combined rhythmite data give a mean rate of lunar recession of 1 24 0 71 cm yr during most of the proterozoic 2450 620 ma suggesting that a close approach of the moon did not occur during earlier time concentrated study of precambrian tidal rhythmites promises to illuminate the evolving dynamics of the early earth moon system and may permit the lunar orbit to be traced back to near the time of the moon s origin

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

lithospheric deformation induced by loading of the hawaiian islands and its implications for mantle rheology the long term rheological properties of the lithosphere are fundamental for understanding both surface tectonics and mantle dynamics on earth in this study we have developed 3 d finite element models for computing the load induced surface deformation and stress for lithosphere and mantle with realistic nonlinear viscoelastic rheology including the frictional sliding low temperature plasticity and high temperature creep we have determined the lithospheric deformation and stress due to volcano loading in the hawaiian islands region for the last few million years by comparing model predictions with seismic observations of the depth to the top of oceanic crust and depth dependence of seismicity in the hawaiian islands region we have sought to constrain lithospheric rheology our calculations show that the load induced surface deformation is controlled by low temperature plasticity and frictional sliding but is insensitive to high temperature creep lithospheric strength predicted from laboratory derived low temperature plasticity needs to be reduced significantly and a frictional coefficient f ranging from 0 1 to 0 7 is required in order to account for the observations however f 0 1 weakens the shallow part of the lithosphere so much that it causes the minima in strain rate and stress to occur at too large depths to be consistent with the observed depth distribution of seismicity our results therefore suggest a value for f between 0 25 and 0 7 finally the maximum stress that accumulates in the deformed lithosphere beneath the hawaiian islands is about 100 200 mpa for models that match the observations and this stress may be viewed as the largest lithospheric stress on earth

paleoenvironmental evidence for latest pleistocene sea level fluctuations on the new jersey outer continental shelf combining high resolution sequence stratigraphy and foraminiferal analysis foraminiferal assemblages in vibracored sediments within 5 m of the seafloor document high resolution sea level fluctuations and confirm the complex quaternary depositional history of the new jersey margin biostratigraphic data have been integrated with ongoing 2 d 3 d high resolution seismic analyses to interpret paleoenvironments of surficial stratigraphy beneath the modern middle to outer shelf cluster analysis of foraminiferal assemblages sampled every 20 cm average define four sample groups a d dominated by benthic species group a characterized by cibicides lobatulus is a middle to outer shelf assemblage 60 100 m water depths group b is composed of middle shelf species 30 60 m water depths and is characterized by low abundances and a fairly uniform distribution of foraminifera which suggests reworking and or a high rate of sediment accumulation group c dominated by elphidium excavatum is an inner to middle shelf assemblage 10 40 m water depths group d present in only one core and dominated by ammonia beccarii represents marginal marine environments 0 10 m water depths with fluctuations in salinity in general the modern sedimentary veneer i e the upper 20 cm is characterized by the deeper water fauna of group a sediments below these modern deposits are characterized by groups b and c reflecting shallower water depths and variable sediment accumulation rates on the inner and middle shelf taken together the group succession in the cores suggests an overall se to nw landward transgression in these latest pleistocene holocene deposits seismic analysis indicates that one core 27 penetrates the flank of a buried channel including its fill and the pre channel section within the channel three alternations of groups c and d suggest fluctuations between marginal marine and middle shelf paleoenvironments high frequency perhaps very small 10 m changes in base level are indicated using previously published ams 14c dates these fluctuations can be constrained as having occurred between 45 000 yr b p channel incision and 12 500 yr b p channel filling suggesting the non uniform nature of the last wisconsinan deglaciation

inner forearc sequence architecture in response to climatic and tectonic forcing since 150 ka hawke s bay new zealand the influence of eustasy tectonic deformation and sediment flux as controlling parameters on basin stratigraphy and depositional sequence development are largely accepted eustasy is usually considered as the dominant mechanism of sequence generation especially for pleistocene successions in active subduction margin settings the high rates of tectonic deformation are expected to have a stronger influence on basin fill architecture while sediment flux is generally less well constrained and therefore less frequently considered the active hikurangi subduction margin in new zealand offers the opportunity to quantitatively assess the relative roles of tectonic climatic and eustatic drivers we present a quantitative source to sink like study of the late pleistocene succession from the hawke s bay sector of the inner forearc domain c 150 ka to present the interpretation of a grid of high resolution marine seismic data onland and offshore core and well descriptions and the integration of geomorphic studies enabled identification of system tracts in turn these comprise two sea level cycle depositional sequences lps1 and lps2 including one complete 100 ka sequence lps1 isopach maps of both sequences reveal changes in sediment distribution and preservation that reflect the relative roles of tectonic deformation and eustasy eustasy dominates development of sequence architecture at relatively short time scales i e 100 kyrs four long lasting depocenters are identified over the inner forearc domain and located in four subsiding basins kidnappers mahia lachlan and motu o kura basins significant shifts of the depocenter location in the basins are correlated with eustatic sea level changes estimates of sediment volumes and masses from isopach maps indicate higher mass accumulation rates during climato eustatic extremes which we correlated to the onland erosional response sediment distribution and landscape evolution are strongly influenced by the interaction of the structural deformation and sediment flux we present paleogeographic reconstructions for the inner forearc domain coincident with two paleoclimatic extremes last glacial maximum and holocene optimum these illustrate the importance of eustatic changes structural deformation and sediment flux on the pattern of sediment distribution accumulation and sequence architecture

the lunar mascons revisited the entire spectra of the surface topography and gravity field of lunar mascons are well presented by the high resolution clementine data the negative correlation between the topography and gravitational potential of the mascons suggests that they are dynamically supported both elastic support and viscous decay models are examined for the elastic support models the spectral characteristics and the lateral variations of the thickness of the elastic layer are determined on the basis of the thin spherical shell flexure formulation and using only the antivarying harmonics of the topography and potential an elastic layer thickness of about 50 km is required to support imbrium serenitatis and nectaris mascons about 35 km for crisium mascon and about 30 km for smythii and humorum mascons a layer of about 20 km thickness can support orientale mascon the strength envelopes of the upper 100 km of the moon within 4 3 gyr ago show that the elastic layer was not thick enough to support the mascons in the early history they decayed through viscous deformation of the lunar interior a lower limit of 6 1024 pa s is estimated for the lunar viscosity within 3 6 3 gyr ago we also determine the thicknesses of the crust and mare flows of the mascon basins on the basis of the assumption that the basins were isostatically compensated prior to the mascon formation the crust beneath the mascon basins is about 30 40 km except for crisium and orientale where the crust is about 20 km the mare flows of about 3 6 km are obtained for almost all of the mascon basins the topography and gravitational potential of aitken basin shows that the basin is compensated at 52 54 km depth the mantle beneath the basin has rebounded upward by about 20 30 km and is overlain by about 20 25 km of a mixture of the excavated crustal and mantle material the lack of a mascon and pervasive mare flows in the basin brings into question the current models of the mascon formation

high frequency stacking pattern and stages of canyon gully evolution across a forced regressive shelf edge delta front abstract the succession of varying facies tracts filling within a canyon or a deep incised gully cutting across the delta front lobes at the shelf edge requires to be explained by high frequency allocyclic and or autocyclic events a fifth and sixth order sequence stratigraphic model for the shelf edge canyon fill or gully fill is here proposed for the first time the first gelasian cold phase and the renewal of transpressional uplift of basin margin occurring at the same time enforced regressive transit of the inner shelf paleo orinoco delta onto the paleo shelf edge its delta front developed along the shoulders of the major successive basin bounding growth faults the delivery of clastic sediments into the deeper slope and beyond in the columbus basin was through the gullies and canyons that incised and cannibalized across the shelf edge delta the mayaro formation of southeast trinidad furnishes the role of growth faulting during the first phase of delta front development at the paleo shelf edge thereby it serves as an example of several fifth order sequences within a fourth order equivalent episode which is contemporaneous to both the glacio eustatic episode the pretiglian and the renewal of transpressional uplift after a pause during the pliocene thus large incision and subsequent filling within the mayaro formation cover a passage of time fifth order equivalent that is unequivocally shorter than the span of the falling pretiglian eustatic sea level and second renewed phase of transpression tectonism the categorization of sedimentary facies of the canyon fill or gully fill and the encasing delta front outside the canyon gully cut into a series of sixth order genetic facies tracts shows variations of geomorphic stages of the canyon gully evolution from accommodation creation to the stages of filling these stages therefore should be attributed to the sixth order equivalent autogenic changes influenced by high frequency growth tectonics instead of assuming the stages to be related to the relatively lower frequency glacio eustatic allocyclicity of the earliest gelasian

late quaternary sequence stratigraphy of a slowly subsiding passive margin new jersey continental shelf high resolution seismic profiles over a 25 000 km2 area off new jersey illustrate the effects of high amplitude high frequency eustasy on a slowly subsiding 0 2 mm yr passive margin analysis of 1600 km of geopulse uniboom minisparker and air gun profiles reveals four depositional sequences with a maximum total thickness of 100 m at the shelf edge correlation of these sequences to biostratigraphic and aminostratigraphic data from drill sites suggests all of these sequences may be post oxygen isotope stage 6 140 ka sequences i and iv appear to correspond to the major glacial interglacial sea level changes 120 m during oxygen isotope stages 6 5 and 2 1 respectively sequences ii and iii reflect smaller scale sea level fluctuations all sequence boundaries are interpreted as type 1 and sequences are predominantly composed of transgressive systems tracts tst and lowstand systems tracts lst much of the tst was deposited as incised valley fills parasequences in the tst commonly are isolated and fragmented the low subsidence rate and high frequency 20 k y eustatic oscillations result in extensive erosion and reworking of previously deposited sediments both by fluvial incision during lowstands and marine erosion during transgressions and highstands on continental margins where subsidence rates and sediment supply are low relative to rates of eustasy sequences are thin fragmented and difficult to correlate local effects such as shifting river drainage salt diapir movements and glacial isostasy can significantly influence sequence preservation on such margins

grail gravity constraints on the vertical and lateral density structure of the lunar crust we analyzed data from the gravity recovery and interior laboratory grail mission using a localized admittance approach to map out spatial variations in the vertical density structure of the lunar crust mare regions are characterized by a distinct decrease in density with depth while the farside is characterized by an increase in density with depth at an average gradient of 35 kg m 3 km 1 and typical surface porosities of at least 20 the apollo 12 and 14 landing site region has a similar density structure to the farside permitting a comparison with seismic velocity profiles the interior of the south pole aitken sp a impact basin appears distinct with a near surface low density porous layer 2 3 times thinner than the rest of the farside this result suggests that redistribution of material during the large sp a impact likely played a major role in sculpting the lunar crust

forced regressions in a sequence stratigraphic framework concepts examples and exploration significance sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level on the shelf lowstand deposits which form during falls and subsequent stillstands of relative sea level can be recognized by the presence of an unconformity at the base the isolated and basinward position relative to the previous shoreline and the abrupt seaward translation of shallow water and shoreline facies into the basin across an unconformity surface this seaward translation of facies and shoreline regression in response to relative sea level lowering is termed a forced regression a forced regression is independent of variations of sediment flux and is in contrast with normal regressions that occur in response to excess sediment flux relative to space available on the shelf i e accommodation forced regressions commonly are associated with a zone of sedimentary bypass subaerial exposure and possible fluvial erosion between the newly formed and preceding shorelines certain shelf sands previously interpreted as offshore or mid shelf sand bodies thus can be reinterpreted as stranded lowstand shorelines associated with forced regressions this alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries with the potential for development of new play types and enhanced recovery in o der fields examples of forced regression can be observed at a variety of scales and ages several such examples include the modern east coulee fan delta and the lower cretaceous viking formation in alberta canada the quaternary rhone delta and the quaternary hudson valley system

coupled thermal orbital evolution of the early moon abstract coupled thermal orbital histories of early lunar evolution are considered in a simple model we consider a plagioclase lid overlying a magma ocean overlying a solid mantle tidal dissipation occurs in the plagioclase lid and heat transport is by conduction and melt migration we find that large orbital eccentricities can be obtained in this model we discuss possible consequences of this phase of large eccentricities for the shape of the moon and geochronology of lunar samples we find that the orbit can pass through the shape solution of garrick bethell et al garrick bethell i wisdom j zuber m 2006 science 313 652 but we argue that the shape cannot be maintained against elastic deformation as the orbit continues to evolve

late quaternary sedimentation on the outer and middle new jersey continental shelf result of two local deglaciations high resolution seismic profiles show two prominent late quaternary sediment wedges on the outer and middle new jersey continental shelf an extensive wedge along the outermost shelf and upper slope up to 50 m thick appears to have been deposited on the hudson apron during an early melting of the late wisconsin laurentide ice sheet subsequent southward transport of this sediment occurred during sea level regression still stand and transgression a mid shelf sediment wedge which forms the fortune shore probably was deposited during a second melt event 11 to 12 ka as sea level was transgressing over the shelf

observations of the r reflector and sediment interface reflection at the shallow water 06 central site acoustic bottom interacting measurements from the shallow water 06 experiment experiment frequency range 1 20khz are presented these are co located with coring and stratigraphic studies showing a thin 20cm higher sound speed layer overlaying a thicker 20m lower sound speed layer ending at a high impedance reflector r reflector reflections from the r reflector and analysis of the bottom reflection coefficient magnitude for the upper two sediment layers confirm both these features geoacoustic parameters are estimated dispersion effects addressed and forward modeling using the parabolic wave equation undertaken the reflection coefficient measurements suggest a nonlinear attenuation law for the thin layer of sandy sediments

lunar orbital evolution a synthesis of recent results the present rate of tidal dissipation in the earth moon system is known to be anomalously high in the sense that the implied age of the lunar orbit is only 1 5 109 years though other evidence suggests an age closer to 4 109 years to assess how long the anomalous dissipation has persisted we use published estimates of lunar orbital configurations derived from a fine grained sediments containing tidal laminations and b numerical ocean models averaged over varying ocean geometries the implied histories of the lunar semimajor axis are surprisingly consistent over the past 109 years the ocean models imply on average reduced dissipation in the past because of a spatial mismatch between tidal forcing and oceanic normal modes of higher frequencies webb s ocean model suggests that the anomalous oceanic dissipation began about 109 years ago and has been increasing since then

late quaternary sedimentation off new jersey new results using 3 d seismic profiles and cores abstract regional seismic reflection surveys have delineated a wedge of late quaternary sediment extending 150 km south from the hudson apron along the edge of the continental shelf off new jersey the bottom of the sediment wedge is defined by a prominent reflector r assumed to represent an erosional surface carved during a low stand of sea level probably corresponding to the wisconsinan maximum glaciation a 3 d reflection survey of a 5 0 5 km area of the southern part of the wedge was carried out in october 1989 line spacing was 10 m and shot spacing 2 5 m navigation achieved position accuracies to the survey shows that the outer shelf sediment wedge has a complex internal structure unrelated to the present seafloor morphology the sedimentary sequence appears to have been formed by a series of depositional events related to glacial melting and interrupted by at least one erosional episode marked by a seismic surface that defines a system of meandering channels faunal studies of samples from cores indicate that the sediments were deposited at shallower depths than at present but there is no evidence for deposition in shallower water or closer proximity to land than the modern mid shelf it appears that the history of periglacial marine sedimentation which accompanied the post wisconsinan deglaciation is no less complex than its continental counterpart

early trace of life from 3 95 ga sedimentary rocks in labrador canada the authors provide evidence for the existence of life on earth in the earliest known sedimentary rocks and suggest that the presence of organic carbon and low stable isotope values of graphite from sedimentary rocks in labrador pushes back the existence of organic life to beyond 3 95 billion years the beginning of organic life on earth is being pushed back by evidence from the earliest known sedimentary rocks tsuyoshi komiya and colleagues argue that the presence of organic carbon and stable isotope excursions in graphite from sedimentary rocks in labrador canada pushes back the existence of organic life to more than 3 95 billion years ago together with recent work showing evidence for a diverse range of living organisms around 3 7 billion years ago including stromatolites living in sunlit surface waters and bacteria living in deep sea hydrothermal vents the work shows that life has been around almost as long as there has been a planet that it can call home the vestiges of life in eoarchean rocks have the potential to elucidate the origin of life however gathering evidence from many terrains is not always possible1 2 3 and biogenic graphite has thus far been found only in the 3 7 3 8 ga gigayears ago isua supracrustal belt4 5 6 7 here we present the total organic carbon contents and carbon isotope values of graphite 13corg and carbonate 13ccarb in the oldest metasedimentary rocks from northern labrador8 9 some pelitic rocks have low 13corg values of 28 2 comparable to the lowest value in younger rocks the consistency between crystallization temperatures of the graphite and metamorphic temperature of the host rocks establishes that the graphite does not originate from later contamination a clear correlation between the 13corg values and metamorphic grade indicates that variations in the 13corg values are due to metamorphism and that the pre metamorphic value was lower than the minimum value we concluded that the large fractionation between the 13ccarb and 13corg values up to 25 indicates the oldest evidence of organisms greater than 3 95 ga the discovery of the biogenic graphite enables geochemical study of the biogenic materials themselves and will provide insight into early life not only on earth but also on other planets

the origin of lunar mascon basins high resolution gravity data from the gravity recovery and interior laboratory spacecraft have clarified the origin of lunar mass concentrations mascons free air gravity anomalies over lunar impact basins display bull s eye patterns consisting of a central positive mascon anomaly a surrounding negative collar and a positive outer annulus we show that this pattern results from impact basin excavation and collapse followed by isostatic adjustment and cooling and contraction of a voluminous melt pool we used a hydrocode to simulate the impact and a self consistent finite element model to simulate the subsequent viscoelastic relaxation and cooling the primary parameters controlling the modeled gravity signatures of mascon basins are the impactor energy the lunar thermal gradient at the time of impact the crustal thickness and the extent of volcanic fill

a simple global model of plate dynamics and mantle convection cooling and thickening of lithospheric plates with age and subduction result in large scale horizontal density contrasts tending to drive plate motions and mantle flow we quantify the driving forces associated with these density contrasts to determine if they can drive the observed plate motions first two dimensional models are computed to evaluate the effects of assumed rheologies and boundary conditions we are unable to obtain platelike behavior in viscous models with traction free boundary conditions the piecewise uniform velocities distinctive of plate motion can be imposed as boundary conditions and the dynamic consistency of the models evaluated by determining if the net force on each vanishes if the lithosphere has a newtonian viscous rheology the net force on any plate is a strong function of the effective grid spacing used leading to ambiguities in interpretation incorporating a rigid plastic lithosphere which fails at a critical yield stress into the otherwise viscous model removes these ambiguities the model is extended to the actual three dimensional spherical plate geometry the observed velocities of rigid plastic plates are matched to the solution of the viscous stokes equation at the lithosphere asthenosphere boundary body forces from the seismically observed slabs from the thickening of the lithosphere obtained from the actual lithospheric ages and from the differences in structure between continents and oceans are included interior density contrasts such as those resulting from upwellings from a hot bottom boundary layer are assumed to occur on a scale small compared to plate dimensions and are not included the driving forces from the density contrasts within the plates are calculated and compared to resisting forces resulting from viscous drag computed from the three dimensional global return flow and resistance to deformation at converging boundaries the rms residual torque is 30 of the driving torque the density contrasts within the plates themselves can reasonably account for plate motions body forces from convection in the interior may provide only a small net force on the plates at converging boundaries the lithosphere has a yield stress of 100 bars drag at the base of the plates is 5 bars and resists plate motion the net driving forces from subducting slabs and collisional resistance are localized and approximately balance driving forces from lithospheric thickening are distributed over the areas of the plates as is viscous drag the approximate balance of these two forces predicts plate velocities uncorrelated with plate area as observed the model represents a specific case of boundary layer convection the dynamical results are consistent with either upper mantle or mantle wide convection

the behavior of the lithosphere on seismic to geologic timescales the strength of the lithosphere and how it responds to loading and unloading are fundamental problems with wide implications flexure studies suggest that the elastic thickness a proxy for the strength of the lithosphere increases with plate age but decreases with load age the elastic thickness is significantly less than the seismic thickness of the lithosphere as indicated by the depth to the low velocity zone suggesting that the lithosphere is a strong structure at short seismic timescales and a weak one at long timescales the mechanism controlling this weakening is not known but it probably involves some form of load induced stress relaxation despite weakening the lithosphere is capable of retaining its strength and supporting loads such as volcanoes and sediments for long periods of geological time lithosphere relaxation should be included in geodynamical models especially as it has impacts on stratigraphy sea level change and dynamic topography

isostasy of the moon from high resolution gravity and topography data implication for its thermal history 1 the lunar prospector line of sight acceleration data after terrain correction have been inverted to the high resolution bouguer gravity anomalies of the lunar nearside lithospheric thicknesses of the early moon were investigated by comparing the gravity anomalies of craters and impact basins of various dimensions the lithosphere was already thick enough to support craters with diameters up to 300 km in the pre nectarian and nectarian periods degree of isostatic compensation of larger impact basins suggested lithospheric thickness of 20 60 km at that time which depended more on localities rather than age differences

stratigraphic organization of late pleistocene deposits of the western part of the golfe du lion shelf languedoc shelf western mediterranean sea using high resolution seismic and core data detailed analysis of shallow penetration single channel seismic data integrated with piston core data reveals that the stratigraphic architecture on the rhone shelf of the western mediterranean sea is characterized by a complex stratigraphy comprising both the regressive and transgressive parts of late pleistocene depositional sequences several cycles of deposition are observed and are interpreted to be associated with fourth or possibly fifth order cycles of relative change of sea level the regressive parts of the sequence are inferred to have been deposited either during late highstand or during periods of relative fall of sea level these deposits are characterized in some instances by discrete downstepping wedges and internal downward shift surfaces however in other instances this evidence is not present the transgressive parts of the depositional sequences are characterized by backstepping wedges and isolated sand bars in general these types of deposits are more common on the western part of the rhone shelf and are largely absent on the extreme eastern part of the shelf the transgressive deposits seem to be preferentially preserved at both inner and outer shelf locations and less so in the middle shelf the exception to this is the area near the rhone delta depocenter where transgressive deposits are observed across the entire shelf key surfaces separating stratigraphic units include ravinement surfaces downlap surfaces and subaerially formed erosional surfaces these stratal discontinuity surfaces constitute the basis for analysis of the stratigraphic architecture this area is dominated by seismic reflection geometries suggesting a high energy depositional environment relatively steeply dipping seismic reflections bounded by horizontal to irregular erosional surfaces characterize most of the upper pleistocene section in this area the high energy seismic facies correspond to three types of deposits 1 thick regressive sands of lobate delta front origin 2 retrogradational beach barriers overlying the regressive wedge on the outer to middle shelf and 3 late transgressive beach sands and ridges observed at the inner shelf the stratigraphic complexity illustrated here is likely analogous to similar although commonly undetected complexity that characterizes petroleum fields in shallow shelf settings a variety of geomorphic elements have been interpreted here these include transgressive sand bars wave dominated distributary mouth bars recurved spits isolated shelf edge shoreface beaches and distributary channels these elements are consistent with an interpretation of a depositional environment characterized by wave dominated delta deposition the morphology of the delta in the eastern part of the shelf i e near the depocenter seems to be consistent from the outer to inner shelf location suggesting that the position of the shoreline relative to the shelf edge and the presence of submerged shelf outboard of the shoreline had only minor impact on deltaic deposition moreover climatic change and changes of fluvial discharge that likely characterized this area during the end page 119 late pleistocene similarly had only minor effect on delta morphology

sequence stratigraphy seismic profiles and cores of pleistocene deposits on the rhone continental shelf abstract high resolution seismic profiles on the rhone deltaic shelf has shown the existence of a complex of pleistocene superimposed prograding wedges interrupted by a major incised valley system cutting across the shelf the individual wedges are interpreted from internal geometry and coring data as prograding shoreface deposits accumulated during periods of relative sea level lowering punctuated by small scale relative sea level falls or forced regressions they are related to 5th order glacio eustatic cycles and are stacked to form a composite 4th order sequence radiocarbon dating tandetron ams of the upper wedge to 40 ka bp indicates a stratigraphic hiatus across the shelf corresponding to the glacial maximum lowstand at the end of the wurmian cycle isotopic stage 2 during which sea level had dropped to 120 m below present sea level seaward tilting of the wedge boundaries indicate that the shelf has been subjected to differential subsidence that provides the necessary accommodation space for deposits to accumulate on the mid outer shelf the seaward tilting results from a cumulative effect of sediment and hydrostatic loading tectonism is also expressed by a westward shore parallel tilting in the area east of the incised valleys the amount of tilting the stacking pattern of the wedges and the location of incised valleys are structurally controlled by the alpine orogen which dips westward under the rhone margin the tectonic component interacts with glacio eustatic sea level fluctuations and accounts for the partition of the shelf into two areas with specific features separated by the rhone incised valleys

significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data how and where the ocean tides dissipate their energy are long standing questions1 that have consequences ranging from the history of the moon2 to the mixing of the oceans3 historically the principal sink of tidal energy has been thought to be bottom friction in shallow seas4 5 there has long been suggestive evidence6 7 however that tidal dissipation also occurs in the open ocean through the scattering by ocean bottom topography of surface tides into internal waves but estimates of the magnitude of this possible sink have varied widely3 8 9 10 11 here we use satellite altimeter data from topex poseidon to map empirically the tidal energy dissipation we show that approximately 1012 watts that is 1 tw representing 25 30 of the total dissipation occurs in the deep ocean generally near areas of rough topography of the estimated 2 tw of mixing energy required to maintain the large scale thermohaline circulation of the ocean12 one half could therefore be provided by the tides with the other half coming from action13 on the surface of the ocean

initial value and modal approaches for transient viscoelastic responses with complex viscosity profiles summary an initial value theory is proposed for studying viscoelastic responses of compressible earth models with complex viscosity profiles continuous spectra are caused by both compressibility and the viscosity stratification and they can cause numerical difficulties for the modal approach we have studied the different responses for various types of viscosity profiles and found that there are differences in the responses at short wavelengths for viscosity profiles with sharp low viscosity zones we found that many modes are required to match the full initial value solutions in the presence of sharp viscosity stratifications in both the upper and lower mantle the normal mode approach is best suited for simple layered models long wavelengths and timescales greater than several thousand years while the initial value approach is indispensable in treating short timescale problems with sharp low viscosity zones in the upper mantle and viscosity stratification in the lower mantle

recent and modern marine erosion on the new jersey outer shelf abstract recent chirp seismic reflection data combined with multibeam bathymetry backscatter and analysis of grab samples and short cores provide evidence of significant recent erosion on the outer new jersey shelf the timing of erosion is constrained by two factors 1 truncation at the seafloor of what is interpreted to be the transgressive ravinement surface at the base of the surficial sand sheet and 2 truncation of apparently moribund sand ridges along erosional swales oriented parallel to the primary direction of modern bottom flow and oblique to the strike of the sand ridges these observations place the erosion in a marine setting post dating the passage of the shoreface ravinement and the evolution of sand ridges that form initially in the near shore environment also truncated by marine erosion are shallowly buried fluvial channel systems formed during the last glacial maximum and filled during the transgression and a regional reflector r that is 40 kyr depths of erosion range from a few meters to 10 m the seafloor within eroded areas is often marked by ribbon morphology seen primarily in the backscatter data as areas of alternating high and low backscatter elongated in the direction of primary bottom flow ribbons are more occasionally observed in the bathymetry where observed crests exhibit low backscatter and troughs exhibit high backscatter sampling reveals that the high backscatter areas of the ribbons consist of a trimodal admixture of mud sand and shell hash with a bimodal distribution of abraded and unabraded sand grains and microfauna the shell hash is interpreted to be an erosional lag while the muds and unabraded grains are in this non depositional environment evidence of recent erosion at the seafloor of previously undisturbed strata the lower backscatter areas of the ribbon morphology were found to be a well sorted medium sand unit only a few 10 s of cm thick overlying the shelly muddy sandy material concentrations of well rounded gravels and cobbles were also found in eroded areas with very high backscatter and at least one of these appears to be derived from the base of an eroded fluvial channel seafloor reworking over the transgressive evolution of the shelf appears to have switched from sand ridge evolution which is documented to 40 m water depth to more strictly erosional modification at greater water depths we suggest that this change may be related to the reduction with water depth in the effectiveness of sediment resuspension by waves resuspension is a critical factor in the grain size sorting during transport by bottom currents over large bedforms like sand ridges otherwise we speculate displacement of sand by unidirectional currents will erode the seafloor

seismic geomorphology of buried channel systems on the new jersey outer shelf assessing past environmental conditions abstract quantitative geomorphologic analysis of shallowly buried dendritic channel systems on the new jersey shelf provides estimates of paleo hydrologic parameters needed to link channel morphology to the former hydrodynamic setting these channels observed in 1 4 khz deep towed chirp seismic data formed presumably as fluvial systems when the shelf was exposed during the last glacial maximum lgm the presumed fluvial origin of these channels is supported by their incision into underlying pleistocene strata a chaotic seismic fill unit at their bases which may be indicative of non marine gravel lag and measured stream junction angles that are consistent with a riverine origin the channels would also have been subjected to estuarine tidal environments during ensuing sea level rise we employ empirically derived hydraulic equations for modern rivers and estuaries to estimate paleo discharges velocities and maximum shear stresses using the preserved and interpolated paleo channel geometries as a guide generally trunk main channels have box like symmetric cross sections with width depth ratios of 100 whereas smaller tributary channels have more v shaped asymmetric cross sections with width depth ratios of 40 70 the high width depth ratios along with low sinuosities 1 1 and slopes

fossil figure contribution to the lunar figure abstract the unusual shape of the moon given its present rotational and orbital state has been explained as due to a fossil figure preserving a record of remnant rotational and tidal deformation jeffreys h 1915 mem r astron soc 60 187 217 lambeck k pullan s 1980 phys earth planet interiors 22 29 35 garrick bethell i wisdom j zuber m t 2006 science 313 652 655 however previous studies assume infinite rigidity and ignore deformation due to changes in the rotational and orbital potentials as the moon evolves to the present state we interpret the global lunar figure with a physical model that takes into account this deformation although the moon deforms in response to rotational and orbital changes a fossil figure capable of explaining the observed figure can be preserved by an elastic lithosphere

long wavelength topographic relaxation for self gravitating planets and implications for the time dependent compensation of surface topography the support of planetary surface topography is controlled by the thickness of the elastic lithosphere and thus has implications for the thermomechanical structure of shallow planetary interiors previous analyses of the support of long wavelength topography have generally utilized elastic formulations which preclude consideration of the time evolution of lithospheric stresses and thermal state here we formulate a viscoelastic model for the support of topography on a spherical planet our stress relaxation model employs a multilayer linear viscoelastic rheology and includes the effect of self gravitation in these models we approximate internal rheology with an olivine flow law and we estimate the internal thermal structure assuming simple conductive cooling we analyze how relief at the surface and internal density interfaces evolves with time in response to a surface or internal load our analysis demonstrates that crustal compensation is strongly dependent on planetary radius with a tendency for a large terrestrial planet like earth to reach complete airy isostasy at long wavelengths within a time scale controlled by the mantle viscosity the correlation of degree of compensation with planetary radius is consistent with previous work turcotte et al 1981 which showed that membrane stress can support significant long wavelength gravity anomalies applied to the moon the degree of compensation associated with loading of 100 ma lithosphere is less than 0 3 and the load love numbers are greater than 0 6 for all harmonics including degree 2 even after 109 years of relaxation this conclusion does not change significantly even with a moderately low viscosity for the crust the tendency for a small body like the moon to support long wavelength stresses may be relevant in understanding the anomalously large degree 2 terms in the lunar shape the results also suggest that major impact basins would not be compensated throughout lunar geological history 4 b y even if the surfaces on which the basins were initially formed were relatively young i e 100 300 ma the fact that the south pole aitken basin is largely compensated suggests that the lateral variations in thermal and or mechanical structure induced by impact processes play significant roles in the compensation of this structure

absorption band q model for the earth body wave surface wave and normal mode data are used to place constraints on the frequency dependence of q in the mantle with a simple absorption band model it is possible to satisfy the shear sensitive data over a broad frequency range the quality factor qs is proportional to in the band and to and 1 at higher and lower frequencies respectively as appropriate for a relaxation mechanism with a spectrum of relaxation times the parameters of the band are q min 80 0 15 and width 5 decades the center of the band varies from 101 seconds in the upper mantle to 1 6 103 seconds in the lower mantle the shift of the band with depth is consistent with the expected effects of temperature pressure and stress high qs regions of the mantle are attributed to a shift of the absorption band to longer periods to satisfy the gravest fundamental spheroidal modes and the scs data the absorption band must shift back into the short period seismic band at the base of the mantle this may be due to a high temperature gradient or high shear stresses a preliminary attempt is also made to specify bulk dissipation in the mantle and core specific features of the absorption band model are low q in the body wave band at both the top and the base of the mantle low q for long period body waves in the outer core an inner core qs that increases with period and low qp qs at short periods in the middle mantle the short period qs increases rapidly at 400 km and is relatively constant from this depth to 2400 km the deformational q of the earth at a period of 14 months is predicted to be 463

tides and the evolution of the earth moon system summary a model of the tides in a hemispherical ocean is used to investigate the effect of changes in the earth s rotation rate on the power dissipated by the ocean tides the results obtained are then used in an idealized astronomical model to investigate how they affect the history of the earth moon system using the tidal model it is found that at rotation rates higher than that of the present earth the power dissipated by the semi diurnal tides in the ocean drops off rapidly as a result of the increased tidal frequency thus if the earth s rotation rate is doubled from its present value then the rate of energy dissipation in the ocean is reduced to approximately one third of its present value and the tidal torque is reduced by a factor of about 6 the present value for secular acceleration of the moon calculated from the results of the tidal model is 30 5 arcsec century 2 using this value in the astronomical model which has the moon and sun in circular orbits above the equator and assuming that the tidal torque is independent of the tidal frequency the gerstenkorn event is predicted to have occurred 1 3 109 yr ago when the astronomical model is run with a torque determined at all times from the tidal model the reduction in the energy dissipated early in the history of the system leads to a gerstenkorn date of 5 3 109 yr ago however dissipation within the solid earth is found to be important early in the history of the system and when this effect is included it gives a date for the gerstenkorn event of 3 9 109 yr ago

the lunar magma ocean reconciling the solidification process with lunar petrology and geochronology abstract the moon is thought to have originated with a magma ocean that produced a plagioclase flotation crust as solidification proceeded ages of anorthositic crust range over at least 200 million years the model for solidification presented here integrates chemical and physical constraints of lunar magma ocean solidification to determine 1 the final thickness of flotation crust generated by a fractionally solidifying magma ocean 2 the timescale of crystallization before plagioclase is a stable phase 3 the timescale of solidification after the formation of the plagioclase flotation crust and 4 the post overturn lunar mantle composition and structure we find that magma oceans of as much as 1000 km depth are consistent with creating an anorthositic crust 40 to 50 km in thickness solidification of the magma ocean prior to formation of the flotation crust may occur on the order of 1000 years and complete solidification would require additional ten to tens of millions of years reconciling these short model timescales with radiometric dates of crustal samples requires either a very late forming moon combined with finding older crustal ages to be incorrect or calling on tidal heating of the crust by the early earth to prolong solidification gravitationally driven overturn of cumulates during tidal heating provides a mechanism for creating the compositions and ages of the lunar mg suite of crustal rocks further we find that upon crystallization the moon likely began with an azimuthally heterogeneous gravitationally stable mantle after magma ocean cumulate overturn this result may help explain the experimentally determined origin of picritic glasses at similar depths but from different source materials

the last glacial insights from continuous coring on the new jersey continental shelf abstract sedimentation on the pleistocene new jersey nj shelf is complex and results from the interaction of processes chiefly driven by glacioeustatic change erosion non deposition downcutting and infilling combine to produce a complicated set of reflectors and sedimentary units that are best interpreted in the shallow subsurface with the aid of high resolution seismic reflection profiling the highly variable lithology on the shelf has historically been an impediment to significant core recovery in this challenging environment coring using the ahc 800 drilling system provided continuous downcore recovery at three sites on the outer shelf the sites targeted fluvial incisions channel fill and exposure surfaces associated with glacial lowstands the exceptional cores were analyzed using an integrated approach textural and benthic foraminiferal data were evaluated to determine the environment of deposition and estimate paleodepth carbon dating of wood and shell material provides the temporal framework for interpretation and k ar dating of hornblende crystals provides insights into the source region of sediments our integrated analysis indicates the nj shelf was a dynamic environment from at least 45 ka estimates of sea level from this study are consistent with other studies from the pleistocene nj margin the oldest sediments 36 k y recovered by drilling came from below site 3 and above site 1 r a time transgressive regional unconformity best estimates are for formation of r on the mid shelf between mis3b and the mis3b a transition 45 ka under neritic conditions channels were incised during late mis2 between 30 and 16 ka channel infill was focused in a narrow time frame during latest mis 2 16 14 ka shortly after the shoreline began to migrate landward rates of 1 2 cm yr are consistent with modern fluvial estuarine sedimentation rates reinvigoration and infilling of the channels around 14 ka is associated with meltwater pulse 1a we find no evidence at our study area for jokelhlaup deposition associated with the intra allerod cold period 13 ka regional deposition channel infill and interfluvial regions was underway by latest mis2 early mis1 as sea level transgressed the shelf the uppermost sediments are of holocene to recent age and are routinely and likely rapidly reworked eroded and mixed by shelf processes the sediment source during mis3 as determined by hornblende age dates was bimodal older sediments were derived from the reading prong nj highlands and younger sediments were sourced from along the hudson river delivery to the study area was through a more southerly paleo hudson position that may have resulted in formation of the outer shelf wedge through deltaic sedimentation during at least mis 3b 3a

basal inflection controlled shelf edge wedges off new jersey track sea level fall a key marker for examining the latest pleistocene history of the new jersey margin is the high amplitude long recognized r horizon reflector this time transgressive surface was formed 47 33 ka and represents the integrated topographic and bathymetric surface developed during the complicated sea level oscillation associated with the regression that preceded the last glacial maximum lgm from landward to seaward across the outer shelf the r reflector changes from subhorizontal in most locations 9 m beneath the modern seafloor to seaward dipping forming the base of two offlapping sediment wedges the previously described outer shelf wedge and a deep shelf wedge seaward of it this transition occurs across two inflection zones where the dip of the r reflector steepens seaward that can be traced for tens of kilometers along strike and mark the landward limits of these wedges these inflection zones are possibly former wave dominated shorefaces these represent the primary topographic elements present during the last regression we speculate that these inflections dictated both the locations for deposition of the two prograding offlapping wedges that developed during the complex sea level fall prior to the lgm and their successive erosion before and after the lgm we suggest that such inflection zones and their associated wedges are important markers of regression in clastic dominated outer shelf settings along passive margins

the role of glacio eustasy in sequence formation mid atlantic continental margin usa abstract previous studies of the mid atlantic continental margin had shown the lack of correlation between pleistocene glacio eustatic oscillations and sequence boundaries this study documents late pleistocene to holocene paleoenvironments within a seismic stratigraphic sequence in order to characterize sequence formation and the development of unconformities in response to glacio eustatic oscillations the data high resolution chirp subbottom profiling and 28 vibracores were collected in water depths of 38 m to 145 m as part of the r v endeavor cruise 370 survey to the mid atlantic continental margin sediment sources sedimentary and seismic facies associated with the last major glaciation and oxygen isotope stages ois 5 to ois 1 were examined and a chronology was constructed from mollusk assemblages of intertidal origin that allowed tracking the paleoshoreline from 19 to 6 ka bp the maximum extent of the last glacial maximum lgm paleoshoreline at 17 ka bp was documented near the 120 m modern isobath the shoreline was marked by sediment mounds up to 5 m high and troughs 15 m deep and 1 km wide interpreted as shoreface and tidal inlet or lagoons formed from 17 to 15 ka bp five kilometers seaward from the lgm shoreline and the head of the hudson canyon is a wedge shaped feature interpreted as a lowstand delta sediments older than the last glacial possibly ois 3 or ois 5 onlap a basal unconformity we correlate this unconformity to a previously identified sequence boundary approximately 20 m to 30 m of sediment accumulated on the outer shelf ne of the hudson canyon during the last glacial and little deposition has occurred since 11 ka bp the modern outershelf is covered by 1 m of mollusk rich glauconitic sand deposited from latest pleistocene to early holocene 15 to 11 ka bp these results showed a close correspondence between depositional environments and glacio eustasy but sequence development and sequence boundary formation appeared to be influenced by the incomplete filling of accommodation space due to poor preservation during ois 2 and low accumulation during the holocene

forced regressive and lowstand hudson paleo delta system latest pliocene growth of the outer new jersey shelf abstract interpretation of the latest pleistocene stratigraphy of the outer new jersey shelf has evolved over the last three decades with addition of new geological and geophysical data during the last decade new results have described and interpreted various depositional elements within the latest pleistocene that overlie the regional reflector known as the r horizon on the basis of observations made from detailed mapping of the r horizon and the overlying sediment wedge s using high resolution shallow seismic chirp data acquired in several phases between 2001 and 2006 we revise the depositional model for the offlapping multi clinothem sediment wedge on the latest pleistocene outer new jersey shelf as strike elongated lobes of a falling stage wave influenced delta system fed by a pre lgm paleo hudson river channel s that probably reached the late pleistocene shelf edge off new jersey this sediment wedge is composed of a series of prograding and offlapping clinothems of varying thickness within our data which does not extend to the basinward termination of the wedge we seldom observe preserved topsets of these clinothems parts of the foresets of some clinothems are also not preserved particularly in the proximal part of the wedge the sediment wedge is elongated in strike direction nne ssw which suggests along strike sediment movement and possible redistribution of sediment in that direction by ambient shore parallel currents our data do not record any time equivalent fluvial channels at the proximal end of the sediment wedge though there are channel features that cap and cut down into several of the clinothems that make up the wedge farther seaward we suggest that this can be explained in two possible ways 1 relatively large spatial separation between the prograding front of the delta system and the delta plain topset deposits as is very common under a falling stage sea level condition and 2 lack of preservation of the stratigraphic record of the delta plain channels because of the likely vigorous falling stage erosion of topsets during the fall of sea level and possibly also during the subsequent transgressive ravinement and flooding after the lgm the clinothems within the sediment wedge show systematic variation in thickness indicating a northward shift of the main depocenter this shift might also be an indication of gradual northward migration of the principal fluvial feeder such a possibility is supported by previously reported late pleistocene paleo hudson channel deposits south of the modern hudson shelf valley