separation of coseismic and postseismic gravity changes for the 2004 sumatra andaman earthquake from 4 6 yr of grace observations and modelling of the coseismic change by normal modes summation eodspatiale grgs for comparison the release 04 solutions of the center for space research csr are also inves tigated after a spectral windowing or a gaussian spatial smoothing results are shown both in terms of geoid height changes and gravity variations coseismic and postseismic gravitational changes estimated from the different gravity solutions are globally similar although their spa tial extent and amplitude depend on the type of filter used in the processing of grace fields the highest signal to noise ratio is found with the grgs solutions the postseismic signature has a spectral content closer to the grace bandwidth than the coseismic signature and is therefore better detected by grace the coseismic signature consists mainly of a strong gravity decrease east of the sunda trench in the andaman sea a gravity increase is also detected at a smaller scale west of the trench the model for the coseismic gravity changes agrees well with the coseismic signature estimated from grace regarding the overall shape and orientation location with respect to the trench and order of magnitude coseismic gravity changes are followed by a postseismic relaxation that are well fitted by an increasing expo nential function with a mean relaxation time of 0 7 yr the total postseismic gravity change consists of a large scale positive anomaly centred above the trench and extending over 15 of latitude along the subduction after 26 months the coseismic gravity decrease has been partly compensated by the postseismic relaxation but a negative anomaly still remains south of phuket a dominant gravity increase extends over 15 of latitude west of the trench being maximal south of the epicentre area by investigating analyses of two global hydrology models and one ocean general circulation model we show that our grace estimates of the coseismic and postseismic gravitational changes are almost not biased by interannual variations originat ing from continental hydrology and ocean circulation in the subduction area and in the central part of the andaman sea while they are biased by several gal in the malay peninsula

a geodynamic model of mantle density heterogeneity using cenozoic and mesozoic plate motion reconstructions we derive a model of present day mantle density heterogeneity under the assumption that subducted slabs sink vertically into the mantle the thermal buoyancy of these slabs is estimated from the observed thermal subsidence cooling of oceanic lithosphere slab velocities in the upper mantle are computed from the local convergence rate we assume that slabs cross the upper lower mantle interface and continue sinking into the lower mantle with a reduced velocity for a velocity reduction factor between 2 and 5 our slab heterogeneity model is as correlated with current tomographic models as these models are correlated with each other we have also computed a synthetic geoid from our density model for a viscosity increase of about a factor of 40 from the upper to lower mantle our model predicts the first 8 spherical harmonic degrees of the geoid with statistical confidence larger than 95 and explains 84 of the observed geoid assuming that the model c21 and s21 terms are absent due to a long relaxation time for earth s rotational bulge otherwise 73 of the geoid variance is explained the viscosity increase is consistent with our velocity reduction factor for slabs entering the lower mantle since downwelling velocities are expected to scale roughly as the logarithm of viscosity loge 40 3 7 these results show that the history of plate tectonics can explain the main features of the present day structure of the mantle the dynamic topography induced by this heterogeneity structure consists mainly of about 1 km amplitude lows concentrated along the active continental margins of the pacific basin our model can also be used to predict the time variation of mantle heterogeneity and the gravity field we find that the age of the geoid defined as the time in the past before which the geoid becomes uncorrelated with the present geoid is about 50 m y our model for the history of the degree 2 geoid which is equivalent to the history of the inertia tensor should give us a tool to study the variations in earth s rotation pole indicated in paleomagiietic studies

the geomorphic impact of glaciers as indicated by tors in north sweden aurivaara 68 n abstract geomorphological investigations carried out on 15 tor like features located on the aurivaara plateau north sweden 68 n provide new insights in the greatly debated age of these landforms erratics and till trapped deep in the tor joints support a pre weichselian age for tor formation moreover the occurrence of various weathering stages in allochtonous material the joint width up to 1 5 m requiring long term weathering and the frequent association of tors with pediment like forms suggest pre quaternary tor formation the juxtaposition of fresh erratics and in situ old weathering features mushroom rocks concentrically weathered well rounded corestones and grus indicates a predominantly cold based regime for the scandinavian ice sheet with erratics carried by the overlying moving ice being repeatedly deposited on tor summits during deglaciation phases the relationships between tors and ice action indicated for the aurivaara plateau result in the proposal of a morphodynamical succession of five tor subtypes ranging from the preservation of well rounded corestones still embedded in grus suggesting negligible glacial erosion to the almost complete removal of tor features by ice scouring a comparison with tors in similar geological and topographical contexts from the unglaciated dartmoor area allows a tentative evaluation of an average overall glacial erosion of 0 10 m on the northern sweden plateaus in sharp contrast with the 190 m overdeepening of the nearby tornetrask basin thus this case study of swedish tors provides additional support to the recent interpretations of relict landscapes in previously glaciated areas and is in accordance with the classical model of glacial selective erosion established in the nordic and arctic mountains

sub aerial denudation of passive margins regional elevation versus local relief models abstract variations in denudation rates which are an important factor in the modification of the sub aerial topography of passive margins have frequently been modelled as being proportionate to regional elevation to be valid this assumption requires that mean slope gradient and the related property of local relief show a strong positive relationship to regional elevation since slope angle is a primary determinant of denudation rate analysis of the relationships between these variables based on the 1 250 000 scale topographic map coverage of southern africa demonstrates that regional modal elevation explains only 0 5 of the variance in mean sine slope gradient and only 0 14 of the variance in local relief measured over 15 15 areas these results demonstrate that regional elevation cannot be used to predict denudation rates for passive margins such as those of southern africa where a dissected coastal zone is separated from a high interior plateau by a major escarpment on the basis of a previous regression analysis relating local relief to sediment and solute transport by rivers the data for southern africa indicate denudation rates of 80 m ma 1 over much of the coastal zone and 1 across most of the elevated interior extrapolation of these results over geological time however necessitates either assumptions about the local relief of palaeotopography or independent evidence of long term denudation rates

relict non glacial surfaces in formerly glaciated landscapes abstract relict non glacial surfaces occur within many formerly glaciated landscapes and contain important information on past surface processes and long term landscape evolution relict non glacial surfaces are distinguishable from glacial surfaces by large scale morphologies including rounded summits fluvial valleys and cryoplanation terraces and pediments and the presence of tors blockfields and or saprolites preservation during glaciation occurs either through coverage by non erosive cold based ice or as nunataks although surface morphologies and denudation rates indicate a continuous non glacial surface history since preglacial times relict non glacial surfaces are dynamic features that have evolved during the quaternary depending on spatial variables such as lithology slope regolith depth and the abundance of fine matrix and water some surfaces are denuding very slowly while others display more rapid denudation high spatial variability in denudation rates results in changing surface morphologies over time denudation rates also display high temporal variability with much surface evolution having perhaps occurred soon after the initial onset of glaciation or during paraglacial phases while some parts of non glacial landscapes are currently active others may be largely inactive relicts of past higher energy regimes although non glacial surfaces are dynamic much remains to be determined regarding surface denudation rates and the magnitude of morphological changes over time

flow unit concept integrated approach to reservoir description for engineering projects abstract the successful application of secondary and tertiary oil recovery technology requires an accurate understanding of the internal architecture of the reservoir engineers have difficulty incorporating geological heterogeneity in their numerical models for simulating reservoir behavior the concept of flow units has been developed to integrate geological and engineering data into a system for reservoir description a flow unit is a volume of the total reservoir rock within which geological and petrophysical properties that affect fluid flow are internally consistent and predictably different from properties of other rock volumes i e flow units flow units are defined by geological properties such as texture mineralogy sedimentary structures bedding contacts and the nature of permeability barriers combined with quantitative petrophysical properties such as porosity permeability capillarity and fluid saturations studies in the subsurface and in surface outcrops have shown that flow units do not always coincide with geologic lithofacies the flow unit approach provides a means of uniquely subdividing reservoirs into volumes that approximate the architecture of a reservoir at a scale consistent with reservoir simulations thus reservoir engineers can incorporate critical geological information into a reservoir simulation without greatly increasing the complexity of their models this approach has advantages over more traditional methodsmore of reservoir zonation whereby model layers are determined on the basis of vertical distributions of permeability and porosity from core analyses and wireline logs less

a source model for the great 2011 tohoku earthquake mw 9 1 from inversion of grace gravity data abstract the co seismic slip distribution of the 2011 tohoku megathrust earthquake is constrained from geoforschungszentrum gfz gravity recovery and climate experiment grace level 2 data time series and our self gravitating compressible 1 d earth model after spatial localization of space gravity data in the surrounding of the u s geological survey usgs epicenter by means of orthogonal slepian functions we estimate the long wavelength co seismic gravity signature the pattern is bipolar the positive pole off shore in the pacific ocean 3 6 gal and the negative pole in the northern japan and japan sea 8 6 gal inversion of the grace data resolves average features of finite fault models the total seismic moment 5 3 1 10 22 nm corresponding to m w 9 1 in agreement with the centroid moment tensor solution the rake angle 87 9 and the mean position of the slip distribution on the fault plane we obtain that the mean depth of the rupture is 17 1 5 km just below the moho discontinuity although we cannot exclude that the rupture also extended to shallower crustal layers and deeper within the lithospheric mantle due to the poor resolution of the along dip dimension of the fault

appalachian piedmont landscapes from the permian to the holocene abstract between the potomac and susquehanna rivers and from the blue ridge to the fall zone landscapes of the piedmont are illustrated for times in the holocene late wisconsin early miocene early cretaceous late triassic and permian landscape evolution took place in tectonic settings marked by major plate collisions permian arching and rifting late triassic and development of the atlantic passive margin by sea floor spreading early cretaceous erosion proceeded concurrently with tectonic uplift and continued after cessation of major tectonic activity atlantic outer continental shelf sediments record three major erosional periods 1 late triassic early jurassic 2 late jurassic early cretaceous and 3 middle miocene holocene the middle miocene holocene pulse is related to neotectonic activity and major climatic fluctuations in the piedmont upland the holocene landscape is interpreted as an upland surface of low relief undergoing dissection major rivers and streams are incised into a landscape on which the landforms show a delicate adjustment to rock lithologies the fall zone has apparently evolved from a combination of warping faulting and differential erosion since late miocene the periglacial environment of the late wisconsin and earlier glacial epochs resulted in increased physical erosion and reduced chemical weathering even with lowered saprolitization rates geochemical modeling suggests that 80 m or more of saprolite may have formed since late miocene this volume of saprolite suggests major erosion of upland surfaces and seemingly contradicts available field evidence greatly subdued relief characterized the early miocene time near the end of a prolonged interval of tropical morphogenesis the ancestral susquehanna and potomac rivers occupied approximately their present locations in early cretaceous time local relief may have been as much as 900 m and a major axial river draining both the piedmont and appalachians flowed southeast past baltimore the late triassic landscape was influenced by rift basin development streams drained into a hydrologically closed basin no through flowing rivers seem to have been present a limestone escarpment along the blue ridge may have existed as a consequence of a semi arid climate the permian may have been a time of himalayan like mountains and mountain glaciers streams and glaciers generally flowed southwest and west

cool kaolins in finland we use d h and 18o 16o ratios to explore the age of kaolins on the fennoscandian shield sub cretaceous kaolins in southern scandinavia have isotopic compositions indicative of weathering under warm mean annual temperatures mats of 15 c deep kaolins on the shield surface in finland previously also have been regarded as products of humid tropical weathering of mesoproterozoic to eocene age new oxygen and hydrogen isotope ratios indicate however weathering by cool groundwater under mats of 13 15 c isotope ratios are also not consistent with deep 1 km burial by cover rocks indicating that a very old age for the weathering is unlikely palaeotemperatures are below cretaceous mats yet substantially above plio pleistocene mats comparisons with palaeotemperatures in n europe and around the arctic ocean indicate that the finnish kaolins developed on the shield surface in the palaeogene or alternatively miocene deep weathering was selectively developed in highly fractured shield rocks and took place in response to latest cretaceous and palaeogene uplift and after stripping of palaeozoic cover rocks the cool kaolins in finland indicate that previous routine attributions of kaolinitic weathering products in the geological record to humid tropical environments should be closely scrutinised

deep weathering through time in central and northwestern europe problems of dating and interpretation of geological record abstract upland and shield areas of central and northwestern europe are characterised by an abundance of relict weathering mantles saprolites these saprolites if accurately dated and interpreted may serve as an important complementary source of information about long term environmental history in this paper methods used to establish ages of weathering mantles are reviewed such as stratigraphic and morphostratigraphic dating clay mineral and stable isotope analysis k ar and cosmogenic isotope dating particularly with reference to european examples the record of deep weathering in the mesozoic and cainozoic is examined to explain the peculiarities of the evidence and controls on the changing style of weathering through time weathering has been a continuous process through time but general and local geological conditions have resulted in different ages of preserved mantles an apparent trend from an earlier kaolinitic ferrallitic style of weathering in the mesozoic and early tertiary towards a grussic style by the end of the cainozoic does not only reflect climate change but it is also broadly consistent with tectonic geomorphic history and related changes in land surface stability miocene and plio pleistocene saprolites in particular show that in different geomorphological and lithological circumstances different types of weathering mantles could have evolved

paleozoic stromatactis and zebra carbonate mud mounds global abundance and paleogeographic distribution carbonate mud mounds with zebra and stromatactis structures are present in every paleozoic system and series but are more common in devonian and carboniferous deposits reaching their acme in mississippian system lower carboniferous rocks global distributions illustrate that mud mounds spanned the planet ranging from tropical to polar circles such a wide latitudinal span signifies that they not only grew in and occupied warm depositional environments but also in settings where oceanic waters were cold and seasonally light limited moreover their proliferation during the devonian and carboniferous was at a time when planet wide climatic ice house conditions are thought to have prevailed mud mounds therefore may also be products of cool and cold water carbonate sedimentation

regolith residence time and the concept of surface age of the piedmont peneplain the common upland weathering profile on foliated metamorphic rocks on the appalachian piedmont between alabama and maryland includes a 50 cm 1 m thick clay rich soil b horizon over 10 20 m of saprolite the saprolite retains the volume fabric and structure of the underlying parent rock but has lost about one third of the mass of the parent rock where the saprolite is thickest beneath upland drainage divides those divides are of loow slope and relief the flatness of the piedmont drainage divides provides the appearance of a planation surface of accordant summits or peneplain i interpret this flatness to be the result of three active processes volume reduction during compaction of saprolite into soil loss of mass in dissolved solids draining the soil b horizon and loss of mass from the soil surface by erosion of clay size particles the cumulative effects of these upland processes are to convert saprolite into soil to limit soil thickness and residence time and to limit the age of the oldest residual soils on the surface this results in a continual lowering of the piedmont peneplain surface this interpretation is corroborated by evidence of topographic inversion of fluvial gravels since the miocene near the fall line study of baseflow dissolved solids draining piedmont basins indicates a minimum rate of saprolite production of about 4 m ma 1 this minimum rate of production near the fall line is less than the estimated rate of surface lowering and saprolite consumption during the late tertiary and quaternary periods of topographic inversion measurement of cosmogenic 10be inventories in two 15 20 mores of piedmont upland regolith indicate a minimum residence time of residual soil and saprolite of about 1 ma this indicates a possible maximum rate of saprolite production and erosion of about 20 m ma 1 using the best available evidence therefore the typical piedmont upland regolith has a residence time of between 1 and 5 ma residence times may not be the same everywhere and ages may vary systematically across the surface the geomorphic evidence of topographic inversion and similar regolith profiles in other humid temperate and tropical regions strongly suggests that production and removal of piedmont saprolite has been an ongoing quaternary process and that most of the piedmont regolith is significantly younger than 5 ma independent geophysical evidence suggests that the rate of uplift probably involving tilting of parts of the piedmont blue ridge and valley and ridge has averaged between 5 and 20 m ma 1 through the cenozoic

tide model errors and grace gravimetry towards a more realistic assessment summary the manner in which errors in tide models affect monthly gravity solutions from grace satellite data is re examined we perform a complete simulation of grace gravity estimation including allowance for accelerometer calibrations and satellite state vector adjustment errors in monthly geoid estimates are for most regions of a order of 0 5 mm or roughly 1 cm of equivalent water height when smoothed over radii of 600 km in polar regions where ocean tide models are suspect errors can grow significantly larger over 2 mm in geoid height although over very localized regions errors from diurnal tides tend to cancel but they are not completely eliminated inducing geoid errors of the order of 0 3 mm the currently accepted grace total error budget is roughly an order of magnitude larger than the component arising from tide modelling errors

introduction and background interpretations of landscape change research into the origins of landscape has a long and distinguished tradition in america landscape studies form the core of physical geology while elsewhere the study of landscape development has spread beyond the confines of geology to develop a firmer foothold in the geographical tradition particularly in geomorphology the development of ideas in landscape study has however been neither steady nor sequential it has been characterized instead by several major conceptual shifts interspersed with periods of reinforcement or neglect within geomorphology and certainly within the english speaking world the most important of these shifts occurred in the early 1960s with the move from denudation chronology of landscapes as a core activity to an emphasis on process based investigation of individual landforms in geology the 1960s also marked an important change in perspective publication of plate tectonic theories sea floor spreading continental drift subduction and mountain building had far reaching consequences for all earth science in particular plate tectonics made the study of apparently ancient processes billions of years old applicable to the present day with for example application to earthquake studies whilst the initial shift towards process studies was a response to the desire for a better understanding of the mechanisms driving landscape change it was not long before this goal became relegated in the eyes of many of its practitioners as a consequence process study became an end in itself rather than a means to an end this movement has been reinforced in recent years by a demand for greater relevance from for example research funding bodies resulting in an emphasis on problem solving and wealth generation that has moved away from studies at the landscape scale consequently within geomorphology process studies and applied geomorphology have come to dominate the literature a dominance reinforced by the increasing division and separation of the discipline into process domains such as fluvial and glacial studies this has reached the point where many researchers would now naturally identify themselves as specialists in a particular process rather than as geomorphologists a similar trend can be identified within geology whereby studies of uplift erosion and stability clearly fall into pre plate tectonics and post plate tectonics generations in the 1920s studies of denudation were popular as evidenced by the volume of work conducted in southern england and based largely on observations of palaeovaueys tilted strata and unconformities sediment provenance became important in the 1920s and 1930s and early works on the use of heavy minerals in studies of past erosion were developed by the 1960s geologists were standing back and viewing many processes in terms of their global plate tectonic significance however this emphasis on processes inevitably led to the development of more labour intensive analytical methods as a consequence of which the wider perspective began to be neglected through the 1970s and 1980s therefore studies of uplift developed using methods that determine heating or pressurization of the uplifted rocks thermal estimates of uplift including spore or conodont alteration indexes fluid inclusion studies and diagenetic models were developed together with estimates of pressurization including studies of mineralogy and sonic borehole logs however perhaps the most significant advance in the determination of uplift rates and amounts has been in the field of apatite fission track analysis afta carter 1999 the widespread use of afta in the oil industry has provided large datasets that encompass the offshore basins formerly ignored by those concerned with land erosion buchanan buchanan 1995 studies of erosion and palaeoerosion have also developed from the study of derived clasts to clay minerals and heavy minerals requiring increasingly labourintensive and hence specialist methods to derive local or even regional perspectives specialization clearly has many advantages if however it is allowed to proceed unchecked these advantages eventually come to be outweighed by the effects of an increasingly reductionist approach whereby concentration on small scale studies and the pursuit of ever greater detail detracts from appreciation of the largescale picture and ultimately fragmentation and loss of the subject core clearly the longer this reductionist segregationist approach persists the more difficult it is to define and to justify the existence of the original parent discipline

thermochronological constraints on the long term erosional history of the karkonosze mts central europe abstract a combination of zircon u th he zhe apatite fission track aft and apatite u th sm he ahe thermochronology is used to constrain the long term exhumation and erosional history of the karkonosze mts in north eastern bohemian massif by analyzing samples from the highly elevated summit planation surface zhe ages from the south eastern part of the planation surface are 285 19 295 20 and 308 21 ma indicating that the area remained at temperatures below 190 c since the permian in contrast zhe ages in the western part of the planation surface are mid cretaceous proving that this part was residing at temperatures above 190 c prior to exhumation the exhumation occurred in the late cretaceous as evidenced by aft and ahe ages ranging from 82 5 to 90 8 ma and from 77 5 to 91 6 ma respectively modelled cooling trajectories are characterized by a two stage cooling history fast cooling through the apatite partial annealing zone and helium partial retention zone to surface conditions between 90 and 75 ma and slow cooling or even thermal stagnation from 75 ma to present although our data do not allow us to resolve the age of the planation surface completely we narrowed down the number of explanatory options and propose two alternative solutions for the formation of the planation surface i the planation surface represents the remnant of a permian peneplain which was buried by mesozoic sediments of the central european basin system and was re exposed in the late cretaceous or ii the planation surface formed after 75 ma after termination of a period of massive erosion documented by thermochronological data and by the sedimentary record in adjacent basins cenozoic relief production and uplift of the planation surface evident from regional landforms and the sedimentary record is not recorded by thermochronological data this shows that erosion on the uplifted planation surface since 75 ma was less than 1 2 km

simultaneous inversion for the earth s mantle viscosity and ice mass imbalance in antarctica and greenland redistribution of mass in the earth due to pleistocene deglaciation and to present day glacial melting induces secular changes in the earth s gravitational field the earth is affected today by the former mechanism because of the viscous memory of the mantle and by the latter because of ongoing surface mass redistribution and related elastic response a self consistent procedure allows us to invert simultaneously for the lower and upper mantle viscosity and for the present day mass imbalance in antarctica and greenland using the observed time variations of the long wavelength gravity field from satellite laser ranging slr analyses the procedure is based on our normal mode relaxation theory for the forward modeling and a newly developed inversion scheme based on the levenberg marquardt method we obtain a large viscosity increase across the 670 km depth transition zone separating the upper and the lower mantle with the lower mantle viscosity varying over the range 5 1021 to 1022 pa s and the less resolved upper mantle viscosity of the order of 1020 pa s when antarctica is the only present day source its rate of melting is 240 gt yr 1 corresponding to a sea level rise of 0 7 mm yr 1 when greenland is added as a source of ice loss the rates of melting are 280 gt yr 1 for antarctica and 60 gt yr 1 for greenland corresponding to sea level rises of 0 8 and 0 2 mm yr 1 slr data indicate that ice melting in the polar regions of the earth is ongoing

distributed fault slip model for the 2011 tohoku oki earthquake from gnss and grace goce satellite gravimetry the gravity recovery and climate experiment grace mission launched 2002 and the gravity field and steady state ocean circulation explorer goce mission march 2009 to november 2013 collected spaceborne gravity data for the preseismic and postseismic periods of the 2011 tohoku oki earthquake in addition the dense japan geonet global navigation satellite systems gnss network measured with approximately 1050 stations the coseismic and postseismic surface displacements we use a novel combination of gnss grace and goce observations for a distributed fault slip model addressing the issues with gravimetric and geometric change over consistent time windows our model integrates the coseismic and postseismic effects as we include goce observations averaged over a 2 year interval but their inclusion reveals the gravity change with unprecedented spatial accuracy the gravity gradient grid evaluated at goce orbit height of 265 km has an estimated formal error of 0 20 me which provides sensitivity to the mainly coseismic and integrated postseismic induced gravity gradient signal of 1 03 me we show that an increased resolution of the gravity change provides valuable information with goce gravity gradient observations sensitive to a more focused slip distribution in contrast to the filtered grace equivalent the 2 year averaging window of the observations makes it important to incorporate estimates of the variance covariance of unmodeled processes in the inversion the gnss and grace goce combined model shows a slip pattern with 20 m peak slip at the trench the total gravity change 200 gal and the spatial mapping accuracy would have been considerably lower by omitting the goce derived fine scale gravity field information

migrating pattern of deformation prior to the tohoku oki earthquake revealed by grace data understanding how and when far field continuous motions lead to giant subduction earthquakes remains a challenge an important limitation comes from an incomplete description of aseismic mass fluxes at depth along plate boundaries here we analyse earth s gravity field variations derived from grace satellite data in a wide space time domain surrounding the mw 9 0 2011 tohoku oki earthquake we show that this earthquake is the extreme expression of initially silent deformation migrating from depth to the surface across the entire subduction system our analysis indeed reveals large scale gravity and mass changes throughout three tectonic plates and connected slabs starting a few months before march 2011 before the tohoku oki earthquake rupture the gravity variations can be explained by aseismic extension of the pacific plate slab at mid upper mantle depth concomitant with increasing seismicity in the shallower slab for more than two years after the rupture the deformation propagated far into the pacific and philippine sea plate interiors suggesting that subduction accelerated along 2 000 km of the plate boundaries in march 2011 this gravitational image of the earthquake s long term dynamics provides unique information on deep and crustal processes over intermediate timescales which could be used in seismic hazard assessment deformation migrated from depth towards the surface in the months leading up to the 2011 tohoku oki earthquake according to analyses of satellite gravity data

cenozoic weathering covers in buchan scotland and their significance isolated occurrences of chemically weathered rock or saprolite are common in many formerly glaciated areas around the north atlantic1 6 these pockets of saprolite are widely regarded as remnants of cenozoic deep weathering covers which existed before the first extensive northern hemisphere glaciations at 2 4 myr ref 7 and their apparent survival has long been used as evidence for the local ineffectiveness of glacial erosion2 4 8 9 however the scarcity of correlative deposits means that the age and significance of these fragmented saprolites are uncertain i report here the results of a detailed survey which shows that in buchan scotland a combination of cenozoic tectonic stability and extremely limited pleistocene glacial erosion has allowed the preservation of deep weathering covers of probable miocene to early pleistocene age on a scale not previously reported from any other formerly glaciated area

the phanerozoic cover sequences preserved as xenoliths in the kimberlite of eastern sierra leone sedimentary and volcanic rocks now unrepresented in surface exposure occur as xenoliths in the kimberlite of the koidu district of eastern sierra leone the sedimentary rocks prove on micropalaeontological evidence to have lower palaeozoic stratigraphic age an eastern extension of the ordovician silurian marine transgression on to the leo uplift of the west african craton of some 200 km is indicated the volcanic rocks may belong to the same cycle of surface rock generation or relate to the younger widespread triassic magmatic event

a decadal scale deformation transient prior to the 2011 mw 9 0 tohoku oki earthquake gps time series in northeast japan exhibit nonlinear trends from 1996 to 2011 before the mw 9 0 2011 tohoku oki earthquake after removing reference frame noise we model time series as linear trends plus constant acceleration correcting for coseismic and postseismic effects from the numerous mw 6 5 earthquakes during this period we find spatially coherent and statistically significant accelerations throughout northern honshu large areas of japan outside the tohoku region show insignificant accelerations demonstrating that the observation is not due to network wide artifacts while the accelerations in northern tohoku sanriku area can be explained by decaying postseismic deformation from pre 1996 earthquakes the accelerations in south central tohoku appear unrelated to postseismic effects the latter accelerations are associated with a decrease in average trench normal strain rate and can be explained by increasing slip rate on the japan trench plate interface and or updip migration of deep aseismic slip in the decades before the 2011 tohoku oki earthquake

prevalence of viscoelastic relaxation after the 2011 tohoku oki earthquake seafloor global positioning system observations immediately after the great 2011 tohoku oki earthquake provide unambiguous evidence for the dominant role of viscoelastic relaxation in short term postseismic deformation rather than just afterslip on the fault as is commonly assumed this paper presents revised estimates of the afterslip following the 2011 tohoku oki earthquake based on seafloor gps observations made immediately after the earthquake tianhaozhe sun et al obtain unambiguous evidence for the dominant role of viscoelastic relaxation in short term postseismic deformation rather than elastic afterslip on the fault as is commonly assumed they conclude that models which erroneously assume an elastic earth substantially overestimate afterslip downdip of the rupture zone and underestimate afterslip updip after a large subduction earthquake crustal deformation continues to occur with a complex pattern of evolution1 this postseismic deformation is due primarily to viscoelastic relaxation of stresses induced by the earthquake rupture and continuing slip afterslip or relocking of different parts of the fault2 3 4 5 6 when postseismic geodetic observations are used to study earth s rheology and fault behaviour it is commonly assumed that short term a few years deformation near the rupture zone is caused mainly by afterslip and that viscoelasticity is important only for longer term deformation6 7 however it is difficult to test the validity of this assumption against conventional geodetic data here we show that new seafloor gps global positioning system observations immediately after the great tohoku oki earthquake provide unambiguous evidence for the dominant role of viscoelastic relaxation in short term postseismic deformation these data reveal fast landward motion of the trench area opposing the seaward motion of gps sites on land using numerical models of transient viscoelastic mantle rheology we demonstrate that the landward motion is a consequence of relaxation of stresses induced by the asymmetric rupture of the thrust earthquake a process previously unknown because of the lack of near field observations our findings indicate that previous models assuming an elastic earth will have substantially overestimated afterslip downdip of the rupture zone and underestimated afterslip updip of the rupture zone our knowledge of fault friction based on these estimates therefore needs to be revised

interpretation of interseismic deformations and the seismic cycle associated with large subduction earthquakes abstract the deformations of the overriding and subducting plates during the seismic cycle associated with large subduction earthquakes are modelled using 2d and 3d finite element techniques a particular emphasis is put on the interseismic velocities and on the impact of the rheology of the asthenosphere the distance over which the seismic cycle perturbs significantly the velocities depends upon the ratio of the viscosity in the asthenosphere to the period of the seismic cycle and can reach several thousand km for rheological parameters deduced from the first years of deformation after the aceh earthquake for a same early postseismic velocity a burger rheology of the asthenosphere implies a smaller duration of the postseismic phase and thus smaller interseismic velocities than a maxwell rheology a low viscosity wedge lvw modifies very significantly the predicted horizontal and vertical motions in the near and middle fields in particular with a lvw the peak in vertical velocity at the end of the cycle is predicted to be no longer above the deep end of the locked section of the fault but further away above the continentward limit of the lvw the lateral viscosity variations linked to the presence at depth of the subducting slab affect substantially the results the north south interseismic compression predicted by this preliminary 2d model over more than 1500 km within the sunda block is in good agreement with the pre 2004 velocities with respect to south china inferred from gps observations in thailand malaysia and indonesia in japan before the tohoku earthquake the eastern part of northern honshu was subsiding while the western part was uplifting this transition from subsidence to uplift so far away from the trench is well fitted by the predictions from our models involving a lvw most of the results obtained here in a 2d geometry are shown to provide a good estimate of the displacements for fault segments of finite lateral extent with a 3d spherical geometry as long as the displacements during the seismic cycle are normalised by the coseismic displacement

flow unit modeling and fine scale predicted permeability validation in atokan sandstones norcan east field kansas characterizing the reservoir interval into flow units is an effective way to subdivide the net pay zone into layers for reservoir simulation commonly used flow unit identification techniques require a reliable estimate of permeability in the net pay on a foot by foot basis most of the wells do not have cores and the literature is replete with different kinds of correlations transforms and prediction methods for profiling permeability in pay however for robust flow unit determination predicted permeability at noncored wells requires validation and if necessary refinement this study outlines the use of a spreadsheet based permeability validation technique to characterize flow units in wells from the norcan east field clark county kansas that produce from atokan aged fine to very fine grained quartzarenite sandstones interpreted to have been deposited in brackish water tidally dominated restricted tidal flat tidal channel tidal bar and estuary bay environments within a small incised valley fill system the methodology outlined enables the identification of fieldwide free water level and validates and refines predicted permeability at 0 5 ft 0 15 m intervals by iteratively reconciling differences in water saturation calculated from wire line log and a capillary pressure formulation that models fine to very fine grained sandstone with diagenetic clay and silt or shale laminae the effectiveness of this methodology was confirmed by successfully matching primary and secondary production histories using a flow unit based reservoir model of the norcan east field without permeability modifications the methodologies discussed should prove useful for robust flow unit characterization of different kinds of reservoirs

glacial geomorphology modeling processes and landforms abstract the primary goal of glacial geomorphology is to provide physically based explanations of the past present and future impacts of glaciers and ice sheets on landform and landscape development to achieve this requires the integration of studies of landform with studies of the processes responsible for form development over a wide range of spatial and temporal scales during the twentieth century significant improvements in approaches to recognizing and describing glacial landforms have been matched by impressive advances in understanding and modeling ice flow and glacial erosion and deposition processes at present process models are being tested explicitly in terms of predicting the development of known forms which also provides new insight into the controls on form development evaluations of the implications of deformable beds for process and form development are also being attempted finally we are reassessing long held beliefs about the significance of glacial action in landform development and sediment production as we head towards the twenty first century glacial geomorphology will advance through the use of three dimensional numerical models that include ice flow basal sliding with explicit consideration of deformable beds erosion and deposition processes and underlying material characteristics these models will be used to address form evolution and test process models and will include both the temporal and spatial aspects of form development space based landform recognition as well as the challenges presented by the concerns of global change will place heightened emphasis on large scale problems which will include reexamination of the basic significance of glacial versus nonglacial action in landform development and sediment production

constraints from deep crustal structure on long term landform development of the british isles and eastern united states abstract it is assumed that some major landforms not easily explained by surface geology could be controlled by deep crustal properties the concept was first applied in the british isles and then to the u s atlantic provinces both regions were affected by similar orogenies in late precambrian paleozoic times and presently belong to the passive margins of the north atlantic ocean in both areas the pattern of rifting was greatly influenced by preexisting tectonic fabric of the continental crust in the british isles pre mesozoic structures are cut obliquely by the atlantic margin while in the u s border the present margin is nearly parallel to the paleozoic sutures the british isles were affected by differential block tectonics during the tertiary examples are given of regional scale landforms linked with crustal hinges recent data confirm the great heterogeneity of the crust beneath the british isles each crustal unit has its own isostatic response according to the state of stress and its own dynamic equilibrium between rock resistance erosion processes and uplift rate in the atlantic provinces of the united states the regional physiographic framework is simpler but allochthonous terranes thrust westward over the grenville basement and shelf sediments have buried some major discontinuities in the deep crust reverse faults associated with the nw se compressional stressfield are numerous but cannot explain regional scale landforms like the blue ridge escarpment above the piedmont rock control is not the direct cause of the escarpment the blue ridge from reaches its highest relief where discontinuities in the deep crust interfere with surficial geological features ocean to continent creep processes are suggested to explain the sustained uplift of the appalachian highlands and the relatively stable position of the mountainous front since middle mesozoic times

dolomite reservoirs porosity evolution and reservoir characteristics systematic analyses of the published record of dolomite reservoirs worldwide reveal that the majority of hydrocarbon producing dolomite reservoirs occurs in 1 peritidal dominated carbonate 2 subtidal carbonate associated with evaporitic tidal flat lagoon 3 subtidal carbonate associated with basinal evaporite and 4 nonevaporitic carbonate sequence associated with topographic high unconformity platform margin buildup or fault fracture reservoir characteristics vary greatly from one dolomite type to another depending upon the original sediment fabric the mechanism by which dolomite was formed and the extent to which early formed dolomite was modified by postdolomitization diagenetic processes e g karstification fracturing and burial corrosion this paper discusses the origin of dolomite porosity and demonstrates the porosity evolution and reservoir characteristics of different dolomite types

land surface evolution at the continental time scale an example from interior western australia abstract the interior plateau of western australia in the wiluna meekatharra area is in part an exhumed pre permian surface of low relief and to that extent of gondwana age a lateritic duricrust on interfluvial remnants of an old plateau surface is probably the outcome of several cycles of weathering and stripping rather than of a single geomorphic episode landforms above the old plateau have maintained their relief during this circumdenudation and there is no regional evidence of their isolation by major escarpment retreat a new plateau surface has extended by stripping of saprolite and is an etchplain as also is the old plateau under the genesis postulated the new plateau cycle was initiated by general drainage rejuvenation whilst lateritic weathering still continued but its extension was halted through increasing climatic aridity probably during the miocene

distinguishing coral reef facies from coral bearing open platform facies examples from ordovician ordos basin northwest china abstract fossil coral communities are often simply considered as coral reefs in fact coral bearing communities are not necessarily coral reefs the key criterion is whether the corals are in situ and if they are abundant enough to form topographic relief two outcropped profiles in the western margin of the ordos basin northwestern china drill cores of the lianglitag formation from 4 wells in the tarim basin and 500 large thin sections were examined in this study to reveal the difference between coral reefs and coral bearing carbonate open platform facies in upper ordivician carbonate succession the second layer of the shijiezigou section is massive in internal structure mound like in shape 5 0 m in height and 33 6 m in width and is interpreted as a patch reef in an open platform this layer has a variety of corals that are preserved in situ reef dwelling organisms include dasycladaceans crinoids and gastropods other layers of the section are bedded limestones many of which bear corals and crinoids while others bear dasycladaceans or only the dasycladacea genus vermiporella unlike in the reef the corals in the open platform facies are sparse and generally occur as fragments most of which are not preserved in situ according to the dominant species four communities are distinguished from the shijiezigou section namely the vermiporella community coral community crinoid coral community and dasycladacean crinoid community each of which adapted to some special environmental conditions the patch reef of the shijiezigou section contain abundant and diverse tabulate corals which form bafflestones while stromatoporoids are the primary builders in the platform margin reefs of well tz 822 and the lijiapo section the common biotic components of the open platform of the shijiezigou section and well tz 822 are crinoids and dasycladaceans the restricted platform of the shijiezigou section is dominated by the dasycladacean vermiporella while the organisms of the restricted platform facies in well tz 35 are mainly composed of cyanobacteria ostracods and tetradium like organisms

ocean contribution to seismic gravity changes the sea level equation for seismic perturbations revisited during megathrust earthquakes great ruptures are accompanied by large scale mass redistribution inside the solid earth and by ocean mass redistribution due to bathymetry changes these large scale mass displacements can be detected using the monthly gravity maps of the grace satellite mission in recent years it has become increasingly common to use the long wavelength changes in the earth s gravity field observed by grace to infer seismic source properties for large megathrust earthquakes an important advantage of space gravimetry is that it is independent from the availability of land for its measurements this is relevant for observation of megathrust earthquakes which occur mostly offshore such as the mw 9 2004 sumatra andaman 2010 maule chile and 2011 tohoku oki japan events in broerse et al we examined the effect of the presence of an ocean above the rupture on long wavelength gravity changes and showed it to be of the first order here we revisit the implementation of an ocean layer through the sea level equation and compare the results with approximated methods that have been used in the literature one of the simplifications usually lies in the assumption of a globally uniform ocean layer we show that especially in the case of the 2010 maule earthquake due to the closeness of the south american continent the uniform ocean assumption is not valid and causes errors up to 57 per cent for modelled peak geoid height changes expressed at a spherical harmonic truncation degree of 40 in addition we show that when a large amount of slip occurs close to the trench horizontal motions of the ocean floor play a mayor role in the ocean contribution to gravity changes using a slip model of the 2011 tohoku oki earthquake that places the majority of slip close to the surface the peak value in geoid height change increases by 50 per cent due to horizontal ocean floor motion furthermore we test the influence of the maximum spherical harmonic degree at which the sea level equation is performed for sea level changes occurring along coastlines which shows to be important for relative sea level changes occurring along the shore finally we demonstrate that ocean floor loading self gravitation of water and conservation of water mass are of second order importance for coseismic gravity changes when grace observations are used to determine earthquake parameters such as seismic moment or source depth the uniform ocean layer method introduces large biases depending on the location of the rupture with respect to the continent the same holds for interpreting shallow slip when horizontal motions are not properly accounted for in the ocean contribution in both cases the depth at which slip occurs will be underestimated

postseismic grace and gps observations indicate a rheology contrast above and below the sumatra slab more than 7 years of observations of postseismic relaxation after the 2004 sumatra andaman earthquake provide an improving view on the deformation in the wide vicinity of the 2004 rupture we include both gravity recovery and climate experiment grace gravity field data that show a large postseismic signal over the rupture area and gps observations in the back arc region with increasing time gps and grace show contrasting relaxation styles that were not easily discernible on shorter time series we investigate whether mantle creep can simultaneously explain the far field surface displacements and the long wavelength gravity changes we interpret contrasts in the temporal behavior of the gps grace observations in terms of lateral variations in rheological properties of the asthenosphere below and above the slab based on 1 d viscoelastic models our results support an almost order of magnitude contrast between oceanic lithosphere viscosity and continental viscosity which likely means that the low viscosities frequently found from postseismic deformation after subduction earthquakes are valid only for the mantle wedge next to mantle creep we also consider afterslip as an alternative mechanism for postseismic deformation we investigate how the combination of grace and gps data can better discriminate between different mechanisms of postseismic relaxation distributed deformation mantle creep versus localized deformation afterslip we conclude that the grace observed gravity changes rule out afterslip as the dominant mechanism explaining long wavelength deformation even over the first year after the event

geological modeling for simulation studies reservoir heterogeneity is hierarchical in nature and different levels of reservoir heterogeneity need to be quantified by the reservoir geologist for numerical simulation studies at the largest scale field scale sand body continuity and interconnectedness are the most important parameters at the scale of a reservoir or a genetic sand body areal permeability trends presence and distribution of permeability baffles vertical profiles of permeability and presence of directional permeability within a sand body are the most critical parameters at a smaller scale the influence of cross bedding on displacement processes is shown to be significant and in fact should be assessed to obtain more meaningful results from larger scale simulation models the examples given show some of the effects of the different scales of heterogeneity on fluid flow patterns these examples indicate the degree of detail that must be considered at different scales if simulations are to give meaningful results

variations in the earth s oblateness during the past 28 years 1 analysis of satellite laser ranging slr data indicates that the earth s dynamic oblateness j2 has undergone significant variations during the past 28 years the dominant signatures in the observed variations in j2 are 1 a secular decrease with a rate of approximately 2 75 10 11 yr 1 2 seasonal annual variations with a mean amplitude of 2 9 10 10 3 significant interannual variations with timescales of 4 6 years and 4 a variation with period of 21 years and an amplitude of 1 4 10 10 with minimum in december 1988 two large interannual variations are related to the strong el nino southern oscillation events during the periods of 1986 1991 and 1996 2002 and it appears that another interannual cycle may have started in late 2002 the superposition of the decadal variation on the interannual signal makes the j2 fluctuation appear to be anomalously large during the 1996 2002 period contemporary models of the mass redistributions in the atmosphere ocean and surface water can explain a major part of the 4 to 6 year fluctuations however the cause of the decadal variation remains unknown

seismic architecture of a miocene isolated carbonate platform and associated off platform strata central luconia province offshore malaysia abstract rather than being homogeneous and isotropic many isolated carbonate platforms in the geologic record include internal heterogeneity and complex geometric relations with off platform strata on their flanks to better understand stratal architecture of a miocene isolated platform central luconia offshore malaysia this study integrates core log and seismic data revealing stratal terminations and geometries that define several seismic stratigraphic units a thick in the basal seismic unit the initial deposits of the carbonate buildup is 4 5 km across this thick includes abrupt thinning to the west and east with onlap onto its flanks but continues outside of the survey area to the north and south above a mappable surface a less extensive 2 5 km seismic unit represents a backstepped isolated platform platform stage 1 across a pronounced normal fault on the east southeast margin of the platform occur marked isochron and seismic character changes with thicker carbonates on the downthrown western block the northern and western margins are not faulted a third seismic unit representing a smaller elongate the most marked stratigraphic theme within the isolated platform is the successive backsteps but the pattern is complicated by interactions with the basinal strata superposition and cross cutting relations document that isolated platform sourced flanking beds wings interfinger with basinal clinoforms wedges as defined by geometries on the margins and flanks of platform stages the platform evolution also was influenced markedly by syndepositional structural activity although structural trends changed from the initial buildup to later platform stages the results and comparison with other isolated platforms demonstrate the complex controls on carbonate platform growth and interactions with basinal siliciclastics

dolomite occurrence evolution and economically important associations abstract dolomite is not a simple mineral it can form as a primary precipitate a diagenetic replacement or as a hydrothermal metamorphic phase all that it requires is permeability a mechanism that facilitates fluid flow and a sufficient supply of magnesium dolomite can form in lakes on or beneath the shallow seafloor in zones of brine reflux and in early to late burial settings it may form from seawater from continental waters from the mixing of basinal brines the mixing of hypersaline brine with seawater or the mixing of seawater with meteoric water or via the cooling of basinal brines bacterial metabolism may aid the process of precipitation in settings where sulfate reducing species flourish and microbial action may control primary precipitation in some hypersaline anoxic lake settings dolomite is a metastable mineral early formed crystals can be replaced by later more stable phases with such replacements repeated a number of times during burial and metamorphism each new phase is formed by the partial or complete dissolution of an earlier dolomite this continual re equilibration during burial detracts from the ability of trace elements to indicate depositional conditions and resets the oxygen isotope signature of the dolomite at progressively higher temperatures because subsurface dolomite evolves via dissolution and reprecipitation a bed of dolomite can retain or create porosity and permeability to much greater burial depths and into higher temperature realms than a limestone counterpart dolomitization also creates new crystals with new rhomb growth following the dissolution of less stable precursors repetition of this process without complete pore cementation can generate intercrystalline porosity a number of times in the rock s burial history intercrystalline porosity is a highly interconnected style of porosity that gives dolomite reservoirs their good fluid storage capacity and efficient drainage the fact that many dolomite reservoirs formed via brine reflux means that they sit beneath an evaporite seal in both platform and basinwide evaporite settings the same association of evaporites sulfate source and entrained hydrocarbons means that burial conditions are also suitable for thermochemical sulfate reduction and the precipitation of base metals this tends to occur at higher temperatures 60 c 80 c and so the resulting dolomites tend to be ferroan and consist of saddle shaped crystals

late cenozoic deep weathering patterns on the fennoscandian shield in northern finland a window on ice sheet bed conditions at the onset of northern hemisphere glaciation abstract the nature of the regolith that existed on the shields of the northern hemisphere at the onset of ice sheet glaciation is poorly constrained in this paper we provide the first detailed account of an exceptionally preserved deeply weathered late neogene landscape in the ice sheet divide zone in northern finland we mine data sets of drilling and pitting records gathered by the geological survey of finland to reconstruct regional preglacial deep weathering patterns within a gis framework using a large geochemical data set we give standardised descriptions of saprolite geochemistry using a variant of the weathering index of parker wip as a proxy to assess the intensity of weathering we also focus on mineral prospects and mines with dense pit and borehole data coverage in order to identify links between geology topography and weathering geology is closely linked to topography on the preglacial shield landscape of northern finland and both factors influence weathering patterns upstanding resistant granulite granite gabbro metabasalt and quartzite rocks were associated with fresh rock outcrops including tors or with thin fines values above 3000 and 4000 beneath valley floors developed along mineralised shear and fracture zones weathering penetrated locally to depths of 50 m and included intensely weathered kaolinitic clays with wip fines values below 1000 late neogene weathering profiles were varied in character tripartite clay gruss saprock profiles occur only in limited areas bipartite gruss saprock profiles were widespread with saprock thicknesses of 10 m weathering profiles included two discontinuities in texture materials and resistance to erosion between saprolite and saprock and between saprock and rock limited core recovery when drilling below the soil base in mixed rocks of the tana belt indicates that weathering locally penetrated deep below upper fresh rock layers such deep seated weathered bands in rock represent a third set of discontinuities incipient weathering and supergene mineralisation also extended to depths of 100 m in mineralised fracture zones the thin weathering crusts found extensively beneath till may represent types of early or middle pleistocene palaeosols we confirm that glacial erosion has been very limited

the piedmont landscape of maryland a new look at an old problem the piedmont upland of maryland has been variously interpreted as a peneplain a series of peneplains a surface of marine planation and a landscape in dynamic equilibrium these different perspectives of landform evolution are related to different scales of time and space both equilibrium and episodic erosion features can be recognized in the modern landscape an equilibrium condition is suggested by adjustment of first and second order streams to rock structure and lithology entrenchment of some streams against gneiss domes altitudinal zonation of rock types around gneiss domes correlation of lithology with overburden thickness on uplands decreasing overburden thickness on uplands related to decreasing degree of metamorphism of crystalline rocks and correlation of secondary mineral assemblages with subsurface drainage and slope the long term episodic character of erosion is suggested by clastic wedges on the adjacent coastal plain an upland of low relief that truncates non carbonate rocks of different lithologies isovolumetric chemical weathering of alumino silicate rocks clastic deposition in marble valleys and weathering profile truncation by modern drainage the maryland piedmont may have been an area of positive relief subject to subaerial erosion since triassic and possibly permian time the upland surface preserved in the eastern piedmont developed by the late cretaceous in the interval from the late cretaceous to the late miocene low input of terrigenous sediments to the coastal plain dominance of marine sedimentation and spotty evidence of saprolite formation on crystalline rocks suggest that the maryland piedmont was an area of low relief undergoing intense weathering incised valleys were formed during a cycle of erosion probably initiated in the late miocene and extensive colluvial sediments were deposited on hillslopes by periglacial processes during the pleistocene

gravitational seismology retrieving centroid moment tensor solution of the 2011 tohoku earthquake 1 mass rearrangement within the crust and lithospheric mantle and ocean water redistribution caused by great earthquakes are made visible by their coseismic gravity signature nowadays detectable by the gravity recovery and climate experiment grace space mission here we present a novel procedure for estimating the principal seismic source parameters hypocenter and moment tensor that relies solely on space gravity data from grace applied for the first time to the 2011 tohoku earthquake it yields a seismic source model that is consistent with a thrust earthquake and geological information of the subduction zone it closely resembles the global centroid moment tensor project solution based on the teleseismic wave inversion although the moment magnitude is higher 9 13 0 11 compared to 9 08 and the hypocenter is further offshore by about 40 km within the oceanic plate this procedure will become an important tool in seismology as it complements centroid moment tensor analysis by exploiting the new gravity data from grace

subglacial preservation of valley morphology at amundsenisen western dronning maud land antarctica on the high altitude polar plateau of amundsenisen western dronning maud land east antarctica a subglacial valley with a broad horizontal valley floor interpreted as a sediment floodplain or valley delta was studied by radio echo sounding in addition a small probably glacial valley was mapped within the same subglacial massif basal ice temperatures were calculated using field data on precipitation air temperature and ice sheet thickness discoveries of old landforms which have been preserved more or less intact beneath the former fennoscandian and laurentide ice sheets have received increasing attention during the last decade the aim of this study is to investigate whether preservation of landforms occurs under the east antarctic ice sheet and to discuss under that climatological and glaciological circumstances preservation may take place the results show that the ice sheet covering the investigated localities is frozen to bed and therefore has an insignificant erosional capability the observations suggest that a large scale subglacial sediment deposit and a small valley formed by glacial erosion have survived beneath a cold based ice sheet marginal zone for a long time period the process of glacial preservation recognized for bedrock features and tentatively observed for sediment accumulations should act on similar large scale landforms under any cold based ice sheet present or past on the basis of existing studies of the age and stability of the east antarctic ice sheet a middle pliocene age is suggested for the preserved landforms the presence of the presumed sediment filled valley further indicates that no prolonged periods of basal melting have occurred at the amundsenisen study area during the ice sheet history which includes the quaternary glaciation periods finally calculations of basal temperature for localities at different altitudes within the same subglacial massif were used to demonstrate local altitudinal control of glacial preservation 1997 by john wiley sons ltd

the accumulation of slip deficit in subduction zones in the absence of mechanical coupling implications for the behavior of megathrust earthquakes the distribution of slip during subduction megathrust earthquakes depends on the slip deficit that accumulates on the plate interface prior to the event we develop 3 d finite element models of subduction zones to investigate how locked zones restrict surrounding regions on the plate boundary from sliding what is new is that we quantify the slip around asperities on the megathrust the models show plate interface slip increasing from zero at the edge of a locked zone to the relative plate motion over a distance of 200 km along the megathrust this area of reduced slip accumulates a seismic moment deficit up to 10 times larger than the moment deficit in the asperity alone updip of locked areas slip at the trench can be reduced by more than 50 of the plate motion despite large displacements of the upper plate near the trench this region moves as a semirigid block rupture models of the 2011 tohoku earthquake its tsunami characteristics and geophysical observations near the trench can be interpreted to reflect the consequences of slip deficit accumulated on a low friction interface updip of the seismogenic zone neighboring asperities affect plate interface slip in a nonlinear way multiple asperities have overlapping pseudo coupled regions that may restrict the magnitude of coseismic slip in single asperity ruptures once an earthquake has a rupture length greater than 250 km it may recover the entire accumulated slip deficit this is consistent with the magnitude of coseismic slip in several recent great megathrust earthquakes

the regolith in australia abstract australian regolith materials are described many of which are complex much australian regolith dates back to the tertiary mesozoic or earlier there is a progressive change in the nature of alluvium through the tertiary aridity revealed through sand dunes and evaporites is confined to the quaternary ferricretes and silcretes are formed on lower slopes often followed by inversion of relief tectonic isolation of australia as well as climatic change is responsible for the change in the nature of terrestrial sediments since the cretaceous

broadscale postseismic gravity change following the 2011 tohoku oki earthquake and implication for deformation by viscoelastic relaxation and afterslip the analysis of grace gravity data revealed postseismic gravity increase by 6 gal over a 500 km scale within a couple of years after the 2011 tohoku oki earthquake which is nearly 40 50 of the coseismic gravity change it originates mostly from changes in the isotropic component corresponding to the mrr moment tensor element the exponential decay with rapid change in a year and gradual change afterward is a characteristic temporal pattern both viscoelastic relaxation and afterslip models produce reasonable agreement with the grace free air gravity observation while their bouguer gravity patterns and seafloor vertical deformations are distinctly different the postseismic gravity variation is best modeled by the biviscous relaxation with a transient and steady state viscosity of 1018 and 1019 pa s respectively for the asthenosphere our calculated higher resolution viscoelastic relaxation model underlying the partially ruptured elastic lithosphere yields the localized postseismic subsidence above the hypocenter reported from the gps acoustic seafloor surveying

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

the significance of rock structure lithology and pre glacial deep weathering for the shape of intermediate scale glacial erosional landforms the main landforms within the glacially scoured precambrian rocks of the swedish west coast are closely connected to the principal structural pattern and have lately been explained as mainly a result of etch processes probably during the mesozoic and with a possible second period of etching during the neogene to explore the effect of multiple glacial erosion on the rock surfaces an island with two different lithologies and with striae from different directions was selected for a detailed study focusing on the shape of roches moutonnees air photo interpretation of bedrock lineaments and roches moutonnees combined with detailed field mapping and striae measurements are used to interpret the structural and lithological control on the resulting shape the study reveals a significant difference in shape between roches moutonnees in augen granite and orthogneiss low elongated and streamlined roches moutonnees occur in the gneiss area striated by a late weichselian ice flow from the ne this ice flow is subparallel with both the local dominant trend of topographically well expressed joints and the schistosity of the gneiss frequently there are no signs of quarrying on the lee sides of the gneiss roches moutonnees and hence they resemble the shape of whalebacks or ruwares as typically associated with the exposed basal weathering surface found in tropical areas the granite roches moutonnees were formed by an older ice flow from the ese which closely followed the etched wnw ese joint system of the granite late weichselian ice flow from the ne caused only minor changes of the landforms on the contrary marks of the early ese ice flow are poorly preserved in the gneiss area where it probably never had any large effect as the flow was perpendicular to both schistosity and structures and accordingly also to the pre glacial relief the study demonstrates that coincidence between ice flow direction and pre glacially etched structures is most likely to determine the effects of glacial erosion copyright 2002 john wiley sons ltd

ice age true polar wander in a compressible and non hydrostatic earth summary issues related to long timescale instability in the earth s rotation named true polar wander tpw have continuously been debated after the pioneering works of the sixties we show ice age tpw results from a newly developed compressible model based on the numerical integration in the radial variable of the momentum and poisson equations and on the contour integration in the laplace domain which allows us to deal with the non modal contribution from continuous radial rheological variations we thus fully exploit the long term behaviour of the earth s rotation and we quantify the effects of the compressible rheology compared to the widely used incompressible one we discuss the so called traditional approach to the earth s rotation developed during the eighties and nineties both for ice age and mantle convection tpw and we explain within this approach the sensitivity of twp predictions to the elastic and viscoelastic rheologies of the lithosphere we agree on the necessity to include the effects of the non hydrostatic bulge from mantle convection to obtain realistic ice age tpw rates in the lower mantle viscosity range 1021 1022 pa s as first indicated by mitrovica et al their analysis represents a first attempt to couple the effects on tpw from mantle convection and glacial forcing by including the non hydrostatic bulge due to mantle convection but not the other time dependent driving terms this partial coupling freezes in space the non hydrostatic contribution due to mantle convection thus damping the present day ice age tpw and forcing the axis of instantaneous rotation to come back to its initial position when ice ages started as discussed in mitrovica et al we also describe a peculiar behavior of the new ice age tpw predictions exhibiting a dampened pendulum motion with the axis of instantaneous rotation overcrossing the position it had before ice ages started we argue that a viscoelastic rather than elastic lithosphere should be adopted in the modelling of tpw although on the time of ice ages it is difficult to disentangle the effects of lithospheric rheology and of mantle convection we discuss the implication of self consistent convection calculations of the non hydrostatic contribution and its impact on the long term earth s rotation stability during ice ages the ice age tpw cannot account for more than 70 per cent of the observed one at least for lower mantle viscosities lower than 1022 pa s mantle convection must therefore contribute to the observed tpw

denudation surfaces and tectonics in the southernmost part of the baltic shield abstract the sub cambrian peneplain is a fundamental landform in the scenery of the southernmost baltic shield it had been shaped during an undefined time interval in the late precambrian and became conserved below a cover of cambrian sedimentary rocks after exhumation the peneplain was subjected to further remodelling in the study of the phanerozoic denudational and tectonic history the sub cambrian peneplain forms an important reference surface mesozoic and tertiary denudation surfaces and sediments dominate in the south and reveal the sequence of events later in the phanerozoic

geomorphology of the gran sabana guayana shield southeastern venezuela abstract the forms of the gran sabana have been developed mainly on rocks of the gently folded precambrian roraima group a sequence of quartzites and siliceous conglomerates with intercalated jasper chert arkose siltstone and shale locally intruded by diabase dikes and sills two planation surfaces are preserved on the gran sabana the auyan tepui 2000 2900 m elevation and the wonken 900 1200 m surfaces with a speculative mesozoic initial age they are still extending table mountains dominate the landscape they comprise pediments foothills precipitous scarps hundreds of meters high a rim and a flattish summit the table mountain topography is controlled by joint systems water percolates along joints and bedding planes dissolves the siliceous cement the quartzite disaggregates and large blocks are isolated and collapse accumulating at the foot of the scarps and on top of the table mountain summits the percolating water forms large and intricate cave systems which frequently emerge in the scarp zone as high waterfalls these mark the lowest level of erosion of the table mountains karstic structures are prominent in the summit zone the evolution of the table mountain topography has been controlled by a combination of tectonic structural stratigraphic climatic and temporal factors

the glaciation of dartmoor the southernmost independent pleistocene ice cap in the british isles the granite uplands of dartmoor have traditionally been considered to be relict permafrost and periglacial landscapes that lay beyond the limits of quaternary glaciations but a variety of landform evidence indicates that a plateau icefield existed on the northern part of the moor constituting the southernmost independent ice cap in the british isles overdeepened or weakly u shaped valley segments fringing north dartmoor document an early extensive phase of glaciation but the most convincing landform evidence relates to more recent valley based glacier occupancy a moraine ridge on the slipper stones represents the most unequivocal palaeo glacier on north dartmoor with a palaeo ela of c 460 m above sea level asl although this relates to the youngest and most restricted phase of glaciation a longer term ela is likely to be represented by the corn ridge proto cirque at 370 410 m asl more extensive valley glaciers are recorded in each of the major drainage basins of north dartmoor by arcuate and linear bouldery ridges and hummocky valley floor drift which are interpreted as latero frontal moraines deposited by outlet lobes of a plateau icefield recession of these lobes is marked by inset sequences of such ridges and occasional meltwater channels plateau ice was predominantly thin and protective and snowblow and preferential accumulation in valley heads facilitated the modest glacial erosion and debris transport recorded in the landforms and sediments it is proposed that the highest plateaux have been occupied by ice for the longest cumulative period of time throughout the quaternary average glacial conditions explaining the distribution of different tor types on northern dartmoor this also explains the lack of tors on the most expansive of the highest plateau terrain ice dispersal centres as the product of a average glacial conditions preferentially removing tors or dampening their production rates b the survival of high relief type 1 tors during glaciation if they occupy summits too narrow to develop significant plateau icefields and or ridges that are bypassed by faster moving ice in adjacent deep valleys and c the survival of subdued type 2 tors in areas glaciated less regularly during the quaternary simple ice flow modelling indicates that a plateau icefield type glaciation is required for significant ice flow to occur and confirms thin ice cover in particular on narrow summits thereby supporting the explanation of tor class distribution the modelling allows us to spatially correlate the geomorphological evidence of margin positions into two major stages and further indicates a strong altitude mass balance feedback leading to an ice cap that is not in balance with its climate and with an extent that is limited by the length of the cold phases rather than their severity

weathering mantles and their significance for geomorphological evolution of central and northern europe since the mesozoic abstract weathering mantles saprolites are very widespread in central western and northern europe where they form thick near surface residual deposits often in excess of 50 m they vary in the type of weathering the bedrock lithology involved the topographic setting and the age and stratigraphic context this review paper provides information about the distribution and major characteristics of weathering mantles from a number of key areas including the british isles the central european belt of mid mountains and uplands the scandinavian mountains and the fennoscandian shield it also examines the evidence for weathering etched origin of various landforms including boulders tors inselbergs basins and some regional landforms assemblages major types of regionally important weathering mantles include ferrallitic lateritic saprolites kaolinite rich saprolites sandy to grus mantles and various residuals left after partial dissolution of carbonate rocks although dating of weathering mantles is often circumstantial it appears sufficiently precise to argue for various ages of deep weathering mesozoic pre late cretaceous mantles are particularly widespread but there are also early tertiary and miocene saprolites widely present whilst most grus weathering is likely to be of miocene to pleistocene age individual upland areas have been subjected to multiple episodes of weathering whose legacy is the present day co existence of different weathering products continental and shallow marine deposits around the uplands particularly in the north sea and intra continental graben structures are often dominated by quartz and kaolinite pointing to deeply weathered land surfaces as the source areas and extending the record of weathering on the geological time scale they demonstrate that weathering mantles repeatedly formed and were subjected to erosion and new cycles of weathering were initiated we suggest that deep unroofing of basement structures in many parts of europe has been mainly accomplished by deep weathering and stripping of pre weathered rock the phenomenon of deep weathering has been very important for geomorphology etched landforms vary in size from small residual boulders up to regional characteristic landscapes etchsurfaces such as joint valley landscapes of southern sweden or undulating multi convex and multi concave landscapes of many uplands in central europe deep weathering has played a major part in the geomorphological evolution of europe since at least the late triassic and the concept involving long term etching and stripping provides an appropriate framework to describe and explain both erosional landscapes and sediment features

limestone diagenesis of upper devonian nisku carbonates in the subsurface of central alberta limestone diagenesis of the upper devonian nisku formation in the subsurface of central alberta began syndepositionally most early calcite cements are fibrous bladed and columnar and form isopachous precipitates in primary voids partial syndepositional induration of the lime matrix sand and mud is indicated by angular limestone intraclasts in deposits flanking some buildups hardgrounds and neptunian dikes in the reefal facies some buildups contain intertidal fades possible vadose cements and some early dissolution molds and vugs in their upper parts suggesting shallow influence of meteoric pore waters towards the end of nisku time postdating these features precipitation of fibrous and subequant calcite cements neomorphism mechanical compaction and incipient stylolitization resulted in complete induration and lithification of the buildups and associated marly strata trace element compositions of the various calcites are variable within individual petrographic groups and may have originated from meteoric and or marine phreatic diagenesis however isotopic and petrographic data of most cements suggest marine phreatic diagenesis therefore most cements were probably formed and or recrystallized in pore waters of marine parentage the oxygen isotope data suggest that limestone diagenesis and lithification were essentially completed at a depth of about 300 m this burial depth was achieved near the end of famennian or in early mississippian time

afterslip and viscoelastic relaxation following the 2011 tohoku oki earthquake mw9 0 inferred from inland gps and seafloor gps acoustic data we simultaneously estimate 2 5 years of afterslip and viscoelastic relaxation as well as coseismic slip for the 2011 tohoku oki earthquake displacements at inland gps and seafloor gps acoustic stations are inverted using viscoelastic green s functions for a model with an upper elastic layer and lower viscoelastic substrate the result shows that afterslip is isolated from the rupture area and possibly asperities of historical earthquakes and has almost decayed by 10 september 2013 2 5 years after the main shock the inversion result also suggests that observed landward postseismic displacements at the seafloor gps acoustic stations are caused by the viscoelastic relaxation whereas trenchward displacements at inland stations are mainly an elastic response to afterslip

coseismic gravity changes of the 2011 tohoku oki earthquake from satellite gravimetry 1 the massive tohoku oki earthquake of a moment magnitude mw of 9 0 occurred on 11 march 2011 off the pacific coast of the northeastern japan the mass redistribution in and around the focal region associated with this earthquake was studied using the gravity changes detected by gravity recovery and climate experiment grace satellite after the 2004 sumatra andaman and the 2010 central chile maule earthquakes the present study presents the third case of clear detection of coseismic gravity changes by grace the observed gravity changes were dominated by decrease over the back arc region of 7 gal or less this reflects to a large extent coseismic crustal dilatation of the landward plate they agree well with the changes calculated with the green s function for the realistic earth using fault parameters inferred from coseismic crustal movements the spatial patterns of the gravity changes of these earthquakes are very similar because they are all shallow angle reverse faulting at convergent plate boundaries we found linear relationship between gravity decreases and seismic moments

pervasive subsurface dolomitization of the nisku formation in central alberta abstract the nisku formation in the subsurface of central alberta canada contains pervasive dolomites that occur mainly as a replacement of reefal limestones the degree of pervasive dolomitization increases downdip along a structural homocline from about 25 to 100 vol and associated replacive anhydrites increase from about 5 to 20 vol pervasive dolomites occur as two types one type consists of almost non porous and impermeable mosaics of cloudy crystals that have diameters of 5 300 microns the other type has significant intercrystalline porosity and permeability and consists of cloudy and clear crystals ranging in size from 100 500 microns cathodoluminescence zonation is rare but modulated structures observed with tem are common both types of dolomite have strong xrd ordering refl ctions and are nearly stoichiometric sr concentrations 25 125 ppm increase and mn concentrations 20 400 ppm decrease upwards in several cores the boron contents of both dolomite types 20 50 ppm are enriched relative to other diagenetic phases 18 ppm the sr isotope ratios vary from 0 7089 0 7107 and are enriched relative to devonian and younger seawater oxygen and carbon isotope ratios cluster around 5 8 permil pdb and 2 0 permil pdb respectively and are similar to those of remnant calcites from the combination of stratigraphic petrographic petrophysical and geochemical data it is inferred that both types of matrix dolomite formed contemporaneously from the same fluids in a flow regime with predominantly upward fluid movement at temperatures between about 40 50 c and at burial depths of about 300 1 000 m most anhydrites formed originally as gypsum during the advanced stages and after matrix dolomitization and later recrystallized to the anhydrites now present based on all accumulated data and on mass balance calculations at least two types of subsurface flow could have caused pervasive dolomitization and gypsification anhydritization 1 expulsion of burial compaction water i e chemically modified seawater with or without additional contributions of m bearing formation waters from deeper parts of the basin e g middle devonian brines and 2 thermal convection of formation fluids originally underlying and or overlying the nisku

grus weathering mantles problems of interpretation abstract grus is an ill defined product of deep weathering of coarse grained rocks whose relationships to other weathering changes remain unclear this paper attempts to address this issue by reviewing a number of examples of coarse saprolites from a variety of climatic and topographic settings grus is the category of weathering mantle that possesses the following characteristics sand gravel 75 100 silt clay

porosity permeability relationships in interlayered limestone dolostone reservoirs porosity and permeability data from five carbonate platform successions of different settings ages and burial depths are examined to identify overall similarities and differences in the reservoir quality of interlayered limestones and dolostones each succession consists mainly of limestone and dolostone with subordinate proportions of intermediate partly dolomitized compositions in the three deeply buried platforms the key features are that limestones have much lower average porosity than associated dolostones and that limestones and dolostones show little difference in average permeability for given porosity in contrast the shallowly buried platforms show little difference in average porosity between limestones and dolostones and also display higher average permeability for given porosity in dolostones than limestones these data suggest the following general guidelines for depositional and diagenetic controls on reservoir architecture in carbonates consisting of interlayered limestone and dolostone 1 reservoir compartmentalization by the formation of tight limestone barriers is largely a burial diagenetic process involving calcite cementation locally produced by chemical compaction 2 both the pattern of early dolomitization and the distribution of clay minerals because they influence the localization of chemical compaction are key factors that determine the distribution of tight limestone barriers separating flow units thus the pattern of eventual burial compartmentalization follows a template that is hardwired into the stratigraphic architecture by depositional mineralogy and early diagenesis 3 after burial 2 3 km 1 2 1 8 mi dolostones should not be expected to have higher permeability for given porosity than associated limestones these rules assume dolomitization to occur early relative to chemical compaction which will commonly be the case because of combined hydrologic and mass balance constraints dolomitization and concentration of clay appear linked to cycle and sequence architecture in the present examples and thus may have a useful degree of predictability at least in terms of statistical parameters such as net gross and probability of flow unit thickness distribution

models for landform development on passive margins some implications for relief development in glaciated areas abstract models for pre glacial relief along passive continental margins must reflect the style and rate of uplift and the rates of weathering and erosion during at least the last 100 150 ma passive margins have varied elevation patterns of rifting uplift and flexuring a distinction is recognised between low lying and steeply rising margins the latter associated with major crustal upwarps continuous flexuring of the crust will maintain disequilibrium in weathering systems and known or possible rates of weathering and erosion appear compatible with weathering penetration during uplift under hot humid conditions a rate of weathering of 50 100 mm ka t1 is possible and could produce 15 30 m of saprolite in 1 ma with 70 surface loss while long term denudation rates seldom exceed 40 mm ka 1 deep sandy and corestone profiles in zones of marginal dissection indicate effectiveness of weathering during uplift examples from southern africa southern australia south america and western africa illustrate 4 morpho tectonic settings low elevation with minimum tilt low domal uplift with coastal tilt high elevation steeply arched and high elevation faulted margin with back tilting these examples are compared with higher latitude marginal landscapes in southeastern usa fennoscandia and scotland it is concluded that pre glacial survival implies more than small relict features and includes exhumed surfaces from beneath sedimentary covers basins and troughs following zones of deeper weathering and local planations now warped and elevated to varying heights above which inselbergs are locally common while relict saprolites are found beneath duricrusts in the tropics and strata bound in high latitudes most saprolite is better understood as having a dynamic history throughout the neogene including the quaternary whether in continuously warm or periodically cold climates

application of reservoir geology to enhanced oil recovery from upper devonian nisku reefs alberta canada the upper devonian west pembina reef trend of west central alberta contains recoverable reserves of over 79 106 m3 500 million bbl of oil and 1 4 1010 m3 500 billion ft3 of gas within approximately 50 pinnacle reefs in the nisku formation although the oil is saturated with gas at original reservoir pressure primary depletion would soon lower the reservoir pressure below the bubble point decreasing recovery thus pressure maintenance is applied early in the producing life of the pools through waterflood or miscible flood schemes selection of the appropriate enhanced recovery scheme depends upon the internal flow unit geometry of the reefs the bigoray nisku c pool and the pembina nisku l pool for end members of the reservoir spectrum they can be used as flow unit models in the geological input for reservoir simulation studies the bigoray nisku c pool is dominantly limestone the primary textures well preserved in this reef provide the key to interpreting the relict textures in fully dolomitized reefs a well displayed ecological zonation of rugose corals passes vertically upward into laminar stromatoporoids which in turn pass into solenoporacean algae the coral and stromatoporoid zones each contain two generic flow unit types depending upon the presence or absence of dolomitization the incipient reef facies and the algal cap with associated tidal flat sediments represent two additional flow units due to the presence of horizontal permeability barriers associated with the limestone lithology the pool is developed with a waterflood displacement scheme ultimate recovery is estimated to be on the or er of 0 55 106 m3 3 5 million bbl or 46 of original oil in place ooip the pembina nisku l pool is a completely dolomitized reef representative of the majority of the reefs in the nisku fairway in contrast to the bigoray nisku c pool the complete dolomitization reduces the number of generic reservoir flow units observed in the l pool reef from six to three due to the excellent reservoir quality and absence of horizontal permeability barriers it is being exploited by a vertical miscible flood the nisku l pool is one of the largest pinnacle reefs discovered in the nisku reef fairway and contains an estimated 5 106 m3 31 million bbl ooip ultimate recovery is estimated to be approximately 4 1 106 m3 25 8 million bbl or 82 of ooip

cosmogenic radionuclides from fiord landscapes support differential erosion by overriding ice sheets the interpretation of differentially weathered mountainous areas along the fringes of pleistocene ice sheets is fundamental for determining ice sheet behavior and thickness during the last glaciation two existing interpretations are either that highly weathered uplands remained as nunataks while freshly eroded troughs held outlet glaciers during the last glaciation or that uplands and lowlands were equally covered by ice but that it was differentially erosive as a function of its spatially variable basal thermal regime cosmogenic radionuclide measurements from 33 bedrock samples and 27 upland erratics from differentially weathered fi ord landscapes on northeastern baffi n island shed light on laurentide ice sheet lis dynamics and thickness tors on weathered upland surfaces have minimum 10 be ages between ca 50 and ca 170 ka n 12 whereas the majority of erratics perched in the uplands range from ca 10 to ca 13 ka n 14 indicating that the whole landscape was glaciated during the last glacial maximum lgm glacially sculpted bedrock n 7 near sea level refl ects the age of deglaciation and increasing amounts of isotopic inheritance in highelevation sculpted bedrock n 3 higher elevation intermediately weathered bedrock n 11 and highest elevation intensely weathered bedrock refl ect the weakening of erosive power as the ice sheet transitioned from fi ords to interfi ord plateaus cold based glaciation of uplands was contemporaneous with warm based glaciation in fi ords suggesting the presence of ice streams 26 al and 10 be concentrations measured in 10 bedrock samples indicate that tors have experienced a complex history of alternating periods of exposure burial and limited glacial erosion the paired isotope data reveal a minimum duration of burial of 80 500 k y presumably by cold based ice and indicate that the tors have an age of at least 150 580 ka these data together with other reconstructions of ice streams in the eastern canadian arctic suggest that ice streams were a large infl uence on northeastern lis dynamics throughout the late quaternary thus the northeastern lis was sensitively tied with north atlantic thermohaline circulation and abrupt climate change

grace gravity data help constraining seismic models of the 2004 sumatran earthquake 1 the analysis of gravity recovery and climate experiment grace level 2 data time series from the center for space research csr and geoforschungszentrum gfz allows us to extract a new estimate of the co seismic gravity signal due to the 2004 sumatran earthquake owing to compressible self gravitating earth models including sea level feedback in a new self consistent way and designed to compute gravitational perturbations due to volume changes separately we are able to prove that the asymmetry in the co seismic gravity pattern in which the north eastern negative anomaly is twice as large as the south western positive anomaly is not due to the previously overestimated dilatation in the crust the overestimate was due to a large dilatation localized at the fault discontinuity the gravitational effect of which is compensated by an opposite contribution from topography due to the uplifted crust after this localized dilatation is removed we instead predict compression in the footwall and dilatation in the hanging wall the overall anomaly is then mainly due to the additional gravitational effects of the ocean after water is displaced away from the uplifted crust as first indicated by de linage et al 2009 we also detail the differences between compressible and incompressible material properties by focusing on the most robust estimates from grace data consisting of the peak to peak gravity anomaly and an asymmetry coefficient that is given by the ratio of the negative gravity anomaly over the positive anomaly we show that they are quite sensitive to seismic source depths and dip angles this allows us to exploit space gravity data for the first time to help constraining centroid momentum tensor cmt source analyses of the 2004 sumatran earthquake and to conclude that the seismic moment has been released mainly in the lower crust rather than the lithospheric mantle thus grace data and cmt source analyses as well as geodetic slip distributions aided by gps complement each other for a robust inference of the seismic source of large earthquakes particular care is devoted to the spatial filtering of the gravity anomalies estimated both from observations and models to make their comparison significant

geodetic data inversion using a bayesian information criterion for spatial distribution of fault slip summary we developed a new inversion method to reconstruct static images of seismic sources from geodetic data using akaike s bayesian information criterion abic coseismic surface displacements are generally related with a slip distribution on a fault surface by linear integral equations parametric expansion of the fault slip distribution by a finite number of known basis functions yields a set of observation equations expressed in a simple vector form incorporating prior constraints on the smoothness of slip distribution with the observation equations we construct a bayesian model with unknown hyperparameters the optimal values of the hyperparameters which control the structure of the bayesian model are objectively determined from observed data by using abic once the values of hyperparameters are determined we can use the maximum likelihood method to find the optimal distribution of fault slip we examined the validity of this method through a numerical experiment using theoretical data with random noise we analysed geodetic data associated with the 1946 nankaido earthquake ms 8 2 by using this method the result shows that the fault slip distribution of this earthquake has two main peaks of 4 and 6 m located off kii peninsula and muroto promontory these two high slip areas are clearly separated by a low slip zone extending along kii strait such a slip distribution corresponds with the fact that the rupture process of this earthquake in the western part is notably different from that in the eastern part

limited modification of mid latitude landscapes by ice sheets the case of northeast scotland the paper uses a case study in scotland to examine the amount and processes of landscape modification by quaternary ice sheets there is an inverse correlation between the distribution of landforms of glacial erosion and pre glacial landscape remnants in northeast scotland the implication is that in places ice sheets can preserve a pre glacial landscape unscathed while elsewhere they remove the pre glacial weathered rock the location of glacial protection or erosion is strongly influenced by the topography and its influence on former ice sheet flow and basal thermal regime the classic glacially eroded landscape of areal scouring can be produced by the removal of only 10 50 m of weathered rock furthermore rock basins often regarded as the hallmark of glacial erosion may be directly inherited from the pre glacial pattern of deep weathering

coseismic and postseismic deformation of the 2011 tohoku oki earthquake constrained by grace gravimetry 1 spaceborne gravimetry data from the gravity recovery and climate experiment grace are processed using spatio spectral slepian localization analysis enabling the high resolution detection of permanent gravity change associated with both coseismic and postseismic deformation resulting from the great 11 march 2011 mw 9 0 tohoku oki earthquake the grace observations are then used in a geophysical inversion to estimate a new slip model containing both coseismic slip and after slip the grace estimated moment for the total slip up to the end of july 2011 is estimated as 4 59 0 49 1022 n m equivalent to a composite mw of 9 07 0 65 if the moment for the tohoku oki main shock is assumed to be 3 8 1022 n m the contribution from the after slip is estimated to be 3 0 1021 12 8 1021 n m in good agreement with a postseismic slip model inverted from gps data we conclude that grace data provide an independent constraint to quantify co and post seismic deformation for the tohoku oki event

a new method for the computation of global viscoelastic post seismic deformation in a realistic earth model i vertical displacement and gravity variation summary we introduce a new method by which to compute global post seismic deformation psd in a spherically symmetric self gravitating viscoelastic earth model previous methods are based on simplified earth models that neglect compressibility and or the continuous variation of the radial structure of earth this is because the previous mode summation technique cannot avoid intrinsic numerical difficulties caused by the innumerable poles that appear in a realistic earth model that considers such effects in contrast the proposed method enables both of these effects to be taken into account simultaneously we carry out numerical inverse laplace integration which allows evaluation of the contribution from all of the innumerable modes of the realistic earth model using this method a complete set of green s functions is obtained including functions of the time variation of the displacement gravity change and the geoid height change at the surface for strike slip dip slip horizontal and vertical tensile point dislocations as an earth model we employ the preliminary reference earth model prem and a convex viscosity profile further we investigate the effects of fine layering of the viscoelastic structure and compressibility on a time series of psd using the green s function for a dip slip fault the result indicates that the effect of increasing number of layers is saturated at several tens of layers even when compressibility is taken into account and that the effect of compressibility is detectable with modern observational techniques for a shallower large earthquake mw 8 as an application the psd due to the sumatra andaman islands earthquake mw 9 3 is estimated we show that the rate of post seismic vertical displacement and gravity change is possibly detected in the far field where the epicentral distance exceeds 400 km