long period perturbations in starlette orbit and tide solution continuous and dynamically consistent orbits have been computed using satellite laser ranging slr data to starlette for a one year period during 1976 and 1977 and the three year period from 1983 through 1985 a low degree and order ocean tide solution consisting of a total of 66 tidal parameters from 14 tidal constituents was obtained in a combined solution using both the one and three year starlette orbits an enhanced model of the schwiderski 1980 tide solution was used both as the a priori and the background tide model the model contains 368 tidal coefficients from 21 tidal constituents yearly values for the second degree annual tides sa which produce seasonal variations on the starlette node were obtained also these variations were found to have year to year fluctuations of more than 25 about the mean value and produced significant long period perturbations in the starlette orbit the starlette tide solution is in good agreement with the schwiderski tide solutions and with other satellite solutions including multi satellite tide solutions the average uncertainties are approximately 0 1 cm for the estimated semidiurnal and diurnal tides and 0 4 cm for the long period tides the discrepancies of effective k2 inferred from the starlette tide solution and other tide solutions are less than 0 01 the tide solutions were evaluated using orbit fits of a three year lageos and a one year starlette long arc the results indicate that the starlette tide solution produces significantly improved orbit fits for both lageos and starlette the uncertainties for the estimated tide model coefficients were used to predict tidal errors for the lageos orbit and were found to be consistent with the apparent tidal errors present in this orbit the computed secular change in the moon s mean motion due to tidal dissipation is 24 8 0 8 arc second century2 which is in good agreement with the results obtained from other investigations

development of cleavage in limestones of a fold thrust belt in eastern new york abstract tectonic cleavage has developed in lower devonian limestones of the hudson valley fold thrust belt in new york state morphology and distribution of cleavage in these limestones is controlled by the amount of clay quartz matrix present and by strain only limestones with greater than 10 clay quartz matrix developed widespread cleavage x ray diffraction analyses indicate that the clay matrix was altered during deformation the width of the 001 illite peak in cleaved lime wackestone is less than that in uncleaved lime wackestone from the same stratigraphic level a minimum of 10 clay is necessary to provide interconnectivity between sites of dissolution and the free fluid system preliminary analyses of bulk chemistry indicate that calcite is removed from the local rock system during cleavage development supporting proposals that circulation of fluid through the rock plays a major role in the development of cleavage textural evidence suggests that both pressure solution and free face dissolution contribute to the removal of ions at grain boundaries cross cutting relations indicate that cleavage was initiated early during the development of the fold thrust belt but continued to develop during the late stages of folding

solid pole tide in global gps and superconducting gravimeter observations signal retrieval and inference for mantle anelasticity abstract the mantle anelasticity plays an important role in earth s interior dynamics here we seek to determine the lower mantle anelasticity through the solution of the complex love numbers at the chandler wobble period the love numbers h 21 l 21 21 and k 21 are obtained in the frequency domain by dividing off the observed polar motion or more specifically the pole tide potential from the observed gps 3 d displacement field and sg gravity variation the latter signals are obtained through the array processing method of ose optimal sequence estimation that results in greatly enhanced signals to be extracted from global array data the resultant love number estimates h 21 0 6248 5 e 4 0 013 5 e 3 i l 21 0 0904 8 e 4 0 0008 2 e 3 i 21 1 156 2 e 3 0 003 1 e 3 i and k 21 0 3125 2 e 3 0 0069 3 e 3 i are thus well constrained in comparison to past estimates that vary considerably they further lead to estimates of the corresponding mantle anelastic parameters f r and f i which in turn determines under the single absorption band assumption the dispersion exponent of 0 21 0 02 with respect to the reference frequency of 5 mhz we believe our estimate is robust and hence can better constrain the mantle anelasticity and attenuation models of the earth interior

tectonic stylolites in the undeformed cumberland plateau of southern tennessee abstract numerous tectonic stylolites i e stylolitic planes most of which are nearly vertical and strike about n30e cut through otherwise undeformed carbonates in the cumberland plateau of southeastern tennessee these stylolites confirm previous arguments that tectonic stylolites should form in flat lying strata in front of foldthrust belts the uniform trend of the teeth of the stylolites at n50w to n70w suggests that they formed as the result of alleghanian compression but the stylolites lie beyond the geographic limits of other larger scale alleghanian structures field evidence shows that the monteagle stylolites which are evenly spaced formed along pre existing fractures illustrating that even spacing is not necessarily evidence of self organization

revised predictions of long period ocean tidal effects on earth s rotation rate the rotational response of earth to long period tidal forces embodied in a zonal response function can be expected to vary with frequency because of variable contributions by the oceans mantle and core the zonal response function has been estimated from 9 years of international radio interferometric surveying iris universal time ut1 data and compared with theoretical predictions using a spherical harmonic tide model to compute the oceans dynamic response at semiannual monthly fortnightly and 9 day lunisolar tidal frequencies different amounts of mantle anelasticity have been considered for both the oceanic and solid earth responses predictions have been made assuming axial core mantle coupling which is either complete or absent additionally an extensive recalibration of the ocean model s frictional parameters was performed using constraints derived in part from space92 polar motion data zonal response function predictions have also been made employing this recalibrated ocean tide model our results indicate that any amount of core coupling can be ruled out at a fortnightly period and probably at a 9 day period but not at a monthly period our results also suggest that the mantle responds purely elastically at a 9 day period but may behave increasingly anelastically at longer periods a simple dispersive rule is postulated for periods ranging up to the 14 month chandler wobble period

the fortnightly and monthly tides resonant rossby waves or nearly equilibrium gravity waves abstract the fortnightly and monthly tides are discussed in the light of recent sea level observations and numerical modeling results within the tide gauge network of the low latitude pacific the fortnightly tide is shown to possess a large scale phase lag of roughly 10 40 degrees although the nonequilibrium part of the fortnightly tide is traditionally thought to be dominated by rossby wave dynamics it is shown via global shallow water modeling studies that this large scale phase lag is explicable in terms of remotely forced gravity waves whose origin is mainly in the arctic ocean although future observations outside the low latitude region of the pacific may eventually reveal rossby wave excitation the fortnightly tidal signal in the tide gauge network at hand appears to reveal at most only weak excitation of rossby waves compared to the phase lag due to remotely forced gravity waves the observed monthly tide appears to be only slightly closer to equilibrium than the fortnightly tide the reaso

an analysis of tidal variations in the length of day observations of the length of day lod corrected for the effects of variations in the angular momentum due to changes in wind velocity and atmospheric pressure ocean tide heights and currents and solid earth zonal tides were analyzed the apparent effect of atmospheric angular momentum aam on the astronomically determined lod is found to be much less at the highest frequencies than at lower frequencies for periods shorter than ten days there appears to be essentially no correlation between aam and lod the international earth rotation service iers standards 1992 model for the effects of zonal tides on the earth s rotation which includes ocean tidal effects adequately accounts for the observations of the variations in the length of day with periods between five and 180 days at the present level of accuracy a currently unexplained semi annual variation in the length of day remains but this may be due to the unmodeled effects of stratospheric winds the power spectrum of the remaining variations with periods less than twenty days is essentially that of a white noise process the amplitudes of the remaining unexplained variations in length of day are less than thirty microseconds this paper has been accepted by geophysical journal international for publication

phase relations for high frequency core mantle coupling and the earth s axial angular momentum budget abstract although it has long been thought that dynamical core mantle coupling is necessary for understanding decadal variations in the length of day lod the physics of the coupling mechanism are very poorly constrained there several hypotheses electromagnetic topographic gravitational viscous but it is notoriously difficult to distinguish between them on observational grounds there is both an expectation geophys j int 138 1999 679 and some evidence j geophys res 100 1995 8233 geophys res lett 24 1997a 1799 that there is significant core mantle coupling on much faster timescales down to subannual periods at such frequencies the core would no longer be the dominant driving force for lod but would instead interact with both the mantle and external reservoirs of angular momentum such as the atmosphere and ocean on these much faster timescales it is possible that some information that is obscured on decadal timescales becomes available in particular any characteristic timescales at very short periods may become observable here i examine the angular momentum budget of the earth on subannual to annual timescales for any additional implied constraints on the physics of angular momentum exchange between the core and the mantle i find that the discrepancy between atmospheric angular momentum and mantle angular momentum on timescales where the ocean is thought to be unimportant has a distinctive signature which is difficult to reproduce using simple models of core mantle coupling although an ad hoc frictional model does moderately well rather than indicating simplicity this may instead be symptomatic of great complexity in the physics of the core mantle boundary region

the composition and internal structure of drumlins complexity commonality and implications for a unifying theory of their formation investigation of drumlins is significant to both glaciology and palaeoglaciology but the sheer diversity of their composition and internal structure is often cited as a major obstacle towards a satisfactory unifying explanation of their formation this paper presents the first systematic survey of the vast literature on this subject with the aim of concisely summarising observations and identifying any emergent patterns or commonality that theories of drumlin formation should be able to explain results confirm that investigations are often limited by availability of suitable sediment exposures 40 of studies report data from 5 drumlins and 44 do not specify sample size although borehole data and geophysical techniques can alleviate this problem however it is clear that the constituents of drumlins are incredibly diverse in terms of their composition e g a range of lithologies clast shapes sizes and fabrics structure e g sediments that are sorted homogeneous surface conformable unconformable and evidence of deformation e g ranging from pervasive to non pervasive limited to absent despite this diversity our review leads us to suggest that drumlin composition can be simplified to five basic types i mainly bedrock ii part bedrock part till iii mainly till iv part till part sorted sediments and v mainly sorted sediments this is a potentially significant step in that it reduces the oft cited complexity of drumlin composition and provides a more realistic goal for theories or numerical models of drumlin formation to target the various types can occur within the same drumlin field which leaves us with two possible implications for drumlin formation 1 different types of drumlin are formed seeded by different processes despite being morphologically similar equifinality investigation of drumlin composition may therefore reveal diagnostic processes explanations for these different types of drumlin and we argue that bedrock drumlins are an example 2 a single process occurs across large parts of the ice bed interface to create drumlinised terrain in a variety of sediments investigation of drumlin composition may in this case simply reflect pre existing sediments but importantly the way in which the drumlin forming mechanism modifies is modified by them we argue that the latter simpler explanation applies to all other types of drumlin excluding purely bedrock forms and conclude that the diversity in drumlin composition is no obstacle to a single unifying theory

north sea pole tide dynamics s u m m a r y laplace tide equations ltes augmented to include linear bottom friction and chandler wobble forcing have been solved numerically for the pole tide in the north sea employing realistic bottom topography and geometrical boundaries the motivation for our study is the need to explain observations of enhanced pole tide amplitudes and eastward intensification along the southern boundary of the sea following wunsch 1974 the tidal dynamics are considered to depend on non equilibrium pole tide behaviour at the open northern boundary of the sea with reasonably small bottom friction and open boundary forcing the amplitude of the pole tide in the north sea is found to be close to equilibrium i e the coastal amplitudes do not match the observations however the phase lag obtained is close to those inferred from tide gauge analyses under these conditions the north sea has the potential to dissipate a considerable fraction 25 per cent of chandler wobble energy if much larger bottom friction is considered the resulting pole tide amplitudes are more highly variable within the sea and if the open boundary forcing is also much larger the tidal amplitudes match many of the observations in this case however the tidal currents dissipate an unacceptably huge amount of wobble energy an earlier version of this problem proposed by wunsch 1974 and reconsidered by dickman preisig 1986 in which time independent ltes are postulated in a north sea modelled with analytical bottom topography and a rectangular domainis also fully solved via the method of weighted residuals the solutions include one in which the non equilibrium portion of the tide height is nearly constant all over the domain the corresponding tidal currents are negligibly slow our work points to the importance of realistic bottom topography and coastline geometry in affecting the tidal dynamics such factors to date have not been considered in theoretical analyses of the north sea pole tide the realistic bathymetry and geometry produce a large variability in bottom friction which is inversely proportional to the water depth and thereby generate substantial dynamic behaviour despite the long period of the pole tide we find that these factors significantly enhance the tidal currents and promote an eastward intensification of the non equilibrium tide height near the southern coast

experiments in tidal mass conservation summary a common feature of theoretical ocean tide models is their failure to conserve mass over the oceans this failure distorts the tidal solution and imparts ambiguity to the calculation of tidal effects on gravity crustal loading and earth rotation for example predicted effects of long period tides on rotation could be uncertain by up to 50 per cent in magnitude and 100 per cent in phase using the spherical harmonic tide theory developed by dickman 1989 the influence of various global conservation constraints on the tidal solution is explored an ocean wide mass conservation constraint implemented using lagrange multipliers produces a realistic and significantly more accurate and unambiguous tidal solution

constraints on q at long periods from earth s rotation in this work we assess constant q and frequency dependent q models of mantle anelasticity our assessment uses the degree 2 love numbers we had inferred previously from a comparison of observed and predicted changes in the length of day at monthly fortnightly and nine day lunar tidal periods the comparison accounted for variable contributions to the tidal signals by dynamic oceans and allowed for axial core mantle coupling that was either complete or absent the love number derived from an earlier analysis of the period of the chandler wobble is also employed we find that the similarity of the degree 2 love number inferred at a nine day period to that at seismic frequencies combined with the significant amount of relaxation at the chandler period together imply that q models operating within the seismic band cannot extend all the way to long tidal periods our analysis of q also allows us to refine estimates of the love number at fortnightly and monthly periods

a glaciofluvial origin for drumlins of the livingstone lake area saskatchewan the livingstone lake drumlin field of northern saskatchewan is on the athabasca plains it is draped over high ground underlain by the precambrian athabasca sandstone the drumlins occur in spindle parabolic and transverse asymmetrical forms a map of individual drumlins shows that features of similar form occur together the drumlins are related on a regional scale to even larger landforms there is also an arrangement of drumlins in streams parallel to the assumed flow direction these patterns illustrate spatial organisation of the drumlin forming flows the livingstone lake drumlins are closely related to tunnel valleys large crescentic scours and eskers exposed bedrock reveals widespread scalloping and sichelwannen an argument is made that drumlins are related to these glaciofluvial forms but were created at different times and by different flows than those forming small scale flutings and other lodgment features sediments within the drumlins are mainly primary water sorted deposits some of wh

effect of surface morphology on the dissipation during shear and slip along a rock rock interface that contains a visco elastic core high resolution topography measurements of the vuache sillingy fault alps france reveal a characteristic roughness of the fault zone we investigate the effect of roughness on the rheology of a planar shear configuration by using a model system consisting of a visco elastic layer embedded into a rigid solid the model is discussed in the context of several geological cases a damage fault zone a fault smeared with a clay layer and a shear zone with strain weakening using both analytical approaches and finite element simulations we calculate to linear order the relation between wall roughness and the viscous dissipation in the fault zone as well as the average shear rate

fortnightly earth rotation ocean tides and mantle anelasticity summary this study of the fortnightly mf tide comprises three main topics 1 a new determination of the fortnightly component of polar motion and length of day lod from a multidecade time series of observed space geodetic data 2 the use of the polar motion determination as one constraint in the development of a hydrodynamic ocean model of the mf tide and 3 the use of these results to place new constraints on mantle anelasticity at the mf tidal period our model of the mf ocean tide assimilates more than 14 years of altimeter data from the topex poseidon and jason 1 satellites because the mf altimetric signal to noise ratio is very small it is critical that altimeter data not be overweighted the polar motion data plus tidegauge data and independent altimeter data give useful additional information with only the polar motion putting constraints on tidal current velocities the resulting ocean tide model plus the dominant elastic body tide leaves a small residual in observed lod caused by mantle anelasticity the inferred effective tidal q of the anelastic body tide is 90 and is in line with a frequency dependence with in the range 0 2 0 3

a complete spherical harmonic approach to luni solar tides summary in this work a spherical harmonic theory of ocean tides is presented the theory is based on laplace tide equations modified to include turbulence with constant eddy viscosity linearized bottom friction and oceanic loading and self gravitation variable bathymetry is also treated in harmonic terms and no flow boundary conditions are applied at continental coastlines the tide and boundary constraint equations are reduced to matrix form and solved by a weighted least squares procedure five zonal luni solar tides ranging in period from 14 days to 18 6 yr are investigated using the theory such tides have typically been difficult to compute using traditional numerical approaches the polar motion and changes in the length of day induced by these long period tides are calculated tidal solutions are compared extensively with results from other tidal theories and from recent satellite and sea level observations the greatest limitation to accurate prediction of zonal tides for any theory appears to be the marginal failure of all tide theories to conserve mass globally the use of additional mass constraints may be warranted

determination of oceanic dynamic barometer corrections to atmospheric excitation of earth rotation the excitation of earth s rotation by atmospheric pressure fluctuations on timescales from days to years is modified by the oceanic response to the pressure load that response has often been approximated as a static inverted barometer ib change in sea level but evidence from theory and both tide gauge and altimetric data suggests that the ib poorly models the sea level response at short periods static models also fail to account for the currents induced by the pressure loading the actual dynamic response of the oceans to barometric loads depends on frequency and on the spatial structure of the loading this work presents a green s function approach to determining the rotational effects of that oceanic response the green s functions characterize the rotational effects of the oceanic response to pressure loads described spatially by individual spherical harmonics for each harmonic of forcing they were computed at nine periods ranging from 4 days to 18 years and interpolated at intermediate periods computations were based on solutions to the author s dynamic spherical harmonic ocean tide model the effects on rotation of the dynamic barometer oceanic response are obtained by a convolution type combination of the green s functions with actual atmospheric pressure data results for data spanning the past decade will be illustrated using harmonically decomposed national center for environmental prediction ncep and european centre for medium range weather forecasts ecmwf pressure fields

evidence for excitation of polar motion by fortnightly ocean tides the second degree zonal tide raising potential which is responsible for tidal changes in the earth s rotation rate and length of day is symmetric about the polar axis and hence can excite the earth s polar motion only through its action upon nonaxisymmetric features of the earth such as the oceans ocean tidal excitation of polar motion in the diurnal and semidiurnal tidal bands has been previously detected and examined here the detection of ocean tidal excitation of polar motion in the long period tidal band specifically at the mf 13 63 day and mf 13 66 day tidal frequencies is reported spectra of the space94 polar motion excitation series exhibit peaks at the prograde and retrograde fortnightly tidal periods after removing effects of atmospheric wind and pressure changes an empirical model for the effect of the fortnightly ocean tides upon polar motion excitation is obtained by least squares fitting periodic terms at the mf and mf tidal frequencies to the residual polar motion excitation series the resulting empirical model is then compared with the predictions of two hydrodynamic ocean tide models

the self consistent dynamic pole tide in non global oceans summary fluid dynamic theories of the pole tide are in conflict with pole tide observations the former predict that the oceanic response to the chandler wobble should be nearly static while the latter reveal the tide to possess significant non equilibrium characteristics resolution of the conflict would determine whether mantle anelasticity or non equilibrium oceans is responsible for a measurable contribution to the chandler period it is possible that resolution might be achieved through a more exact mathematical investigation of pole tide fluid dynamics than theories have carried out to date the theories have also neglected to consider a unique property of the pole tide its ability to lengthen the period of its own forcing function this property implies that the pole tide characteristics and effects on wobble cannot be correctly determined unless the tide and wobble equations are jointly solved this work constitutes a first attempt to determine accurately and self consistently the nature of the pole tide and its effects on the chandler wobble the laplace tidal equations modified by the addition of bottom friction but with no simplifying approximations are employed together with the liouville equations to elucidate pole tide characteristics this work is a first attempt because the earth model chosen is a crude one consisting of global oceans of uniform depth overlying a rigid mantle with a fluid core results for this model suggest that departures of the pole tide from equilibrium may indeed be minimal the relevance of these results to the actual pole tide however must await the application of our self consistent and more exact dynamical theory to the situation of realistic oceans

orogeny and stratigraphy numerical models of the paleozoic in the eastern interior of north america a computer model is used to estimate patterns of lithospheric deformation caused by obduction and removal of loads within orogenic belts regions of lithospheric downwarp become sedimentary depocenters and regions of lithospheric upwarp suffer erosion by following the deposition and erosion of sedimentary packages through a number of model time steps it is possible to calculate a synthetic stratigraphy for a given study area this model is applied to the post early ordovician stratigraphy of the eastern interior region of north america the loading that drives lithospheric deformation is associated with the development of the appalachian and ouachita orogens and the independent development of the michigan and illinois intracratonic basins model results are shown to be consistent with presently observed stratigraphy lithology and cumulative erosion and are then used to estimate the configuration of given sediment packages at discrete intervals following their deposition these estimates are presented in the form of isopach maps stratigraphic cross sections and time stratigraphic diagrams as a function of time over the last 470 ma by tracking the burial and erosion history of sedimentary units we are able to establish a cause and effect relationship between particular tectonic events and the extent of preservation of sedimentary units in particular we suggest that the pennsylvanian permian alleghanian orogeny produced major sediment cover over much of the study area

late paleozoic deformation of the cratonic carbonate cover of eastern north america paleozoic carbonates that cover the eastern half of the north american craton preserved a bedding parallel shortening fabric up to 800 km away from the appalachian ouachita orogenic front as recorded by mechanical twins in calcite a strain fabric is present in 29 of 31 samples from three traverse within the flat lying cratonic cover sequence jasper arkansas to minneapolis bluefield west virginia to madison wisconsin and albany new york to hamilton ontario twinning is found only in paleozoic carbonates and is absent in cretaceous limestones in the two southernmost traverses the orientation of the principal shortening axis e1 is perpendicular to the thrust front and parallel to the thrusting direction of the southern appalachians and the ouachitas the magnitude of calcite shortening strain 6 and the calculated differential stress 90 mpa decrease exponentially away from the orogenic front until twinning is absent the northernmost traverse shows greater complexity probably because of its location in the bend of the appalachian trend the authors conclude that the regional strain fabric preserved in the cratonic cover sequence of eastern north american was produced by late paleozoic orogenic stresses of the appalachian ouachita orogeny and that compressive stresses were transmitted over distances greater than 1200 km awaymore from the active plate margin less

spectral and geographical variability in the oceanic response to atmospheric pressure fluctuations as inferred from dynamic barometer green s functions 1 a decade ago a novel theoretical approach was developed dickman 1998 for determining the dynamic response of the oceans to atmospheric pressure variations a response nicknamed the dynamic barometer db and the effects of that response on earth s rotation this approach employed a generalized spherical harmonic ocean tide model to compute oceanic green s functions the oceans fluid dynamic response to unit amplitude pressure forcing on various spatial and temporal scales and then construct rotational green s functions representing the rotational effects of that response when combined with the observed atmospheric pressure field the rotational green s functions would yield the effects of the db on earth s rotation the green s functions reflect in some way the geographical and spectral sensitivity of the oceans to atmospheric pressure forcing we have formulated a measure of that sensitivity using a simple combination of rotational green s functions we find that the db response of the oceans to atmospheric pressure forcing depends significantly on geographic location and on frequency compared to the inverted barometer ib the traditional static model the db effects differ slightly at long periods but become very different at shorter periods among all the responses the prograde polar motion effects are the most dynamic with large portions of the north atlantic and some of the north pacific no larger than one third of ib but most of the southern hemisphere oceans at least 50 greater than ib

rapid soft bed sliding of the puget glacial lobe the puget lobe of the late pleis inferred to be lodgment till based on the tocene cordilleran ice sheet advanced into presence of oriented stones oriented stria western washington over a thick sequence of tions on stones overconsolidation and unlithified sediments the basal drag due to deformation features sliding over this surface was calculated by 1 this paper investigates the rapid motion of idealizing the sediment bed as a rigid planar the puget lobe over its bed of deformable sedi surface scattered with roughness elements cor ment studies of large vanished glaciers com responding to individual sedimentary particles plement basal motion studies of modern glaci and 2 taking the minimum reconstructed slid ers in which the glacier geometry and velocity ing velocity to be 500 m yr 1 the calculated are well constrained but the characteristics of basal drag minimized by choices of parameters the bed can only be inferred from observations is 400 kpa much higher than the reconstructed over very limited areas kamb et al 1985 gravitational driving stress of 40 kpa indi seismic measurements blankenship et al 1986 cating that a rigid bed and low water pressure or modelling lingle and brown 1987 obser are not consistent with the glacierfs rapid vations on glacier beds recently exposed by motion high subglacial water pressure aver glacial retreat can provide information about aging 90 of the ice overburden 10 mpa is conditions during a somewhat greater time span inferred from overconsolidation of subglacial but are restricted to the marginal environ clays the occurrence and deformation of ment in addition inferences about the bed of water deposited sediments within the till and modern glaciers are limited by the short dura the requirement to drain large quantities of tion and seasonality of the observations a water from the interface suggest that water notable benefit of studying the beds of pieis pressure reached 99 of the ice overburden tocene glaciers is that they record basal ploughing of till by ice entrained clasts per conditions for intervals spanning entire glaci vasive shearing and finally ice bed separa ations and accessible far from the glacier tion become possible as water pressure margins increases at the low inferred effective nor after a brief summary of data available from mal stress the basal drag is reduced from the previous reconstructions of the puget lobe the rigid bed case by water layers which decouple basal conditions of the lobe are explored along the smallest particles from the glacier sole two complementary lines we first present cal and ploughing which reduces the resistance culations of basal drag due to glacier sliding offered by the largest particles the limited for different models of till bed roughness that shear strain observed in much of the till indicate that rapid sliding requires very low implies pervasive shearing did not contribute effective stresses and extensive ice bed significantly to ice motion basal motion was decoupling or ploughing second we summarize confined to the ice bed interface or to dis geological and geotechnical data that indicate tinct faults within the substrate

emergent drumlins and their clones from till dilatancy to flow instabilities subglacial bedforms are a range of landforms 10 105 m in length shaped mostly in glacial sediments and are abundant on ice sheet beds numerous explanations for their generation especially of drumlins have been proposed rather than viewing them as resulting from erosion or deposition directly by ice smalley and unwin 1968 proposed that both might occur simultaneously if beneath the glacier a layer of lubricating sediment existed and flowed conducting geomorphic work erosion deposition shaping of its own this idea appears to have steered the field leading perhaps to final resolution of the centuries old problem of drumlin genesis here i trace how the idea evolved leading to the conclusion that subglacial bedforms are emergent phenomena arising from self organisation in the coupled flow of ice sediment and water the ubiquity and patterning of bedforms appears to be well explained by a naturally arising flow instability in the subglacial system and which has been demonstrated by analytical and numerical modelling a problem for the instability theory is an apparent mismatch between predicted and observed sedimentological properties of bedforms a distinction is made between emergent drumlins drumlin clones and obstacle drumlins which helps explain some apparent contradictions and a conceptual framework is erected that might form a basis for confrontation of the theory with the wealth of observational evidence that exists

structural chronology of the alleghanian orogeny in southeastern west virginia the trend change between central and southern appalachian structures is sharply defined in southeastern west virginia there n30 35 e trends coincident with major central appalachian folds such as the browns mountain anticline end abruptly at n60 e trending southern appalachian structures along the st clair fault analysis of local and regional folds cleavage bedding perpendicular stylolite seams and bedding and fault slickenlines reveals that layer parallel shortening directed n10 30 w occurred in nonfolded greenbrier group mississippian carbonates well into the present appalachian plateau area this structural event is early and is associated with the evolution of southern appalachian folds and faults south of the st clair fault central appalachian folds and mesoscopic structures were superimposed on this early layer parallel shortening fabric this structural chronology indicates that southern appalachian folds and faults predated the development of central appalachian structures in the region

the variation with frequency of the long period tides the oceanic response to long period tidal forcing in closed basins approaches equilibrium for periods much longer than a month for moderate values of dissipation at a given frequency the response is closest to equilibrium near the eastern wall of the basin global calculations of the mf and mm tides made using a 2 2 grid are presented changes in the length of day have also been computed for these tides