new global marine gravity model from cryosat 2 and jason 1 reveals buried tectonic structure gravity models are powerful tools for mapping tectonic structures especially in the deep ocean basins where the topography remains unmapped by ships or is buried by thick sediment we combined new radar altimeter measurements from satellites cryosat 2 and jason 1 with existing data to construct a global marine gravity model that is two times more accurate than previous models we found an extinct spreading ridge in the gulf of mexico a major propagating rift in the south atlantic ocean abyssal hill fabric on slow spreading ridges and thousands of previously uncharted seamounts these discoveries allow us to understand regional tectonic processes and highlight the importance of satellite derived gravity models as one of the primary tools for the investigation of remote ocean basins

palaeolatitudinal distribution of lithologic indicators of climate in a palaeogeographic framework whether the latitudinal distribution of climate sensitive lithologies is stable through greenhouse and icehouse regimes remains unclear previous studies suggest that the palaeolatitudinal distribution of palaeoclimate indicators including coals evaporites reefs and carbonates has remained broadly similar since the permian period leading to the conclusion that atmospheric and oceanic circulation control their distribution rather than the latitudinal temperature gradient here we revisit a global scale compilation of lithologic indicators of climate including coals evaporites and glacial deposits back to the devonian period we test the sensitivity of their latitudinal distributions to the uneven distribution of continental areas through time and to global tectonic models correct the latitudinal distributions of lithologies for sampling and continental area bias and use statistical methods to fit these distributions with probability density functions and estimate their high density latitudinal ranges with 50 and 95 confidence intervals the results suggest that the palaeolatitudinal distributions of lithologies have changed through deep geological time notably a pronounced poleward shift in the distribution of coals at the beginning of the permian the distribution of evaporites indicates a clearly bimodal distribution over the past 400 ma except for early devonian early carboniferous the earliest permian and middle and late jurassic times we discuss how the patterns indicated by these lithologies change through time in response to plate motion orography evolution and greenhouse icehouse conditions this study highlights that combining tectonic reconstructions with a comprehensive lithologic database and novel data analysis approaches provide insights into the nature and causes of shifting climatic zones through deep time

a deforming plate tectonic model of the south china block since the jurassic abstract the south china block has experienced multiple phases of tectonic deformation since the middle jurassic understanding this deformation history helps reveal the driving mechanisms responsible and sheds light on the associated magmatism and mineralization here we construct deformable plate tectonic reconstructions for the south china block from 170 ma to the present using gplates the deformation starts with a nw se oriented shortening phase from 170 to 136 ma subsequently south china experienced two episodes of extension in the cretaceous during 136 118 ma and 100 80 ma respectively the cenozoic extension occurred mostly along the southeast continental margin including the east china sea shelf basin and rift basins in the northern south china sea margin and the taiwan margin segment the rifting was initiated nearly simultaneously along the continental margin at 65 ma and ceased at 34 30 ma the northern portion of the okinawa trough started rifting at 15 ma while the southern portion rifted in the last few million years the luzon volcanic arc thrusting onto the southeasternmost south china block since 6 5 ma caused the still active taiwan orogeny the predicted accumulated deformation at present day is characterized by overall shortening onshore with contraction factors mostly between 0 8 and 1 and extension offshore with stretching factors generally between 1 and 2 the central china orogen and taiwan orogen experienced more intense shortening relative to the interior south china by factors down to 0 6 the okinawa trough experienced intense stretching by factors up to 2 5 in its central part the intraplate deformation in the south china block is closely related to the subduction of the izanagi and pacific plates the jurassic and earliest cretaceous shortening was likely induced by trench advance and the extension during the cretaceous and the cenozoic was mostly driven by subduction retreat

the interplay of dynamic topography and eustasy on continental flooding in the late paleozoic abstract global sea level change can be inferred from sequence stratigraphic and continental flooding data these methods reconstruct sea level from peri cratonic and cratonic basins that are assumed to be tectonically stable and sometimes called reference districts and from spatio temporal correlations across basins however it has been understood that long wavelength typically hundreds of km and low amplitude

assimilating lithosphere and slab history in 4 d earth models we develop methods to incorporate paleogeographical constraints into numerical models of mantle convection through the solution of the convection equations the models honor geophysical and geological data near the surface while predicting mantle flow and structure at depth and associated surface deformation the methods consist of four constraints determined a priori from a plate history model 1 plate velocities 2 thermal structure of the lithosphere 3 thermal structure of slabs in the upper mantle and 4 velocity of slabs in the upper mantle these constraints are implemented as temporally and spatially dependent conditions that are blended with the solution of the convection equations at each time step we construct earth like regional models with oceanic and continental lithosphere trench migration oblique subduction and asymmetric subduction to test the robustness of the methods by computing the temperature velocity and buoyancy flux of the lithosphere and slab full sphere convection models demonstrate how the methods can determine the flow associated with specific tectonic environments e g back arc basins intraoceanic subduction zones to address geological questions and compare with independent data both at present day and in the geological past e g seismology residual topography stratigraphy using global models with paleogeographical constraints we demonstrate 1 subduction initiation at the izu bonin mariana convergent margin and flat slab subduction beneath north america 2 enhanced correlation of model slabs and fast anomalies in seismic tomography beneath north and south america and 3 comparable amplitude of dynamic and residual topography in addition to improved spatial correlation of dynamic and residual topography lows

middle miocene tectonic boundary conditions for use in climate models utilizing general circulation models gcms for paleoclimate study requires the construction of appropriate model boundary conditions we present a middle miocene paleotopographic and paleobathymetric reconstruction geographically constrained at 15 ma for use in gcms paleotopography and paleogeography are reconstructed using a published global plate rotation model and published geological data paleobathymetry is reconstructed through application of an age depth relationship to a middle miocene global digital isochron map followed by the overlay of reconstructed sediment thickness and large igneous provinces adjustments are subsequently made to ensure our reconstruction may be utilized in gcms

causes of rapid uplift and exceptional topography of gongga shan on the eastern margin of the tibetan plateau abstract erosion and tectonic uplift are widely thought to be coupled through feedbacks involving orographic precipitation relief development and crustal weakening in many orogenic systems it can be difficult to distinguish whether true feedbacks exist or whether observed features are a consequence of tectonic forcing to help elucidate these interactions we examine gongga shan a 7556 m peak on the eastern margin of the tibetan plateau where cosmogenic 10 be basin wide erosion rates reach 5 mm yr defining a region of localized rapid erosion associated with a restraining bend in the left lateral xianshuihe fault erosion rates are consistent with topography thermochronometry and geodetic data suggesting a stable pattern of uplift and exhumation over at least the past 2 3 my transpression along the xianshuihe fault orographically enhanced precipitation thermally weakened crust and substantial local relief all developed independently in the gongga region and existed there prior to the uplift of gongga shan however only where all of these conditions are present do the observed topographic and erosional extremes exist and their relative timing indicates that these conditions are not a consequence of rapid uplift we conclude that their collocation at 3 4 ma set into motion a series of feedbacks between erosion and uplift that has resulted in the exceptionally high topography and rapid erosion rates observed today

investigating the role of the galicia bank on the formation of the north west iberian margin using deformable plate tectonic models abstract the kinematic evolution of the west iberian margin during the opening of the southern north atlantic has been of interest for several decades and provides a well constrained environment to study and develop new concepts related to the formation of non volcanic magma poor passive margins building upon previous rigid and deformable plate tectonic modelling studies the aim of this work is to create deformable plate tectonic models of the west iberian margin using previously published constraints in gplates to investigate the role of the galicia bank as an independent continental ribbon during deformation of the west iberian margin from 200 ma to present day a comparison of present day crustal thickness results calculated from deformable plate tectonic reconstructions with those obtained from gravity inversion has allowed the plate kinematics of the galicia bank relative to the flemish cap to be investigated additionally this comparison provided detailed insights into the most probable kinematic scenarios for the galicia bank continental ribbon including its impact on the deformation experienced within the galicia interior basin two preferred kinematic models for the galicia bank are proposed one that implies synchronous motion with the flemish cap until 160 ma after which the galicia bank begins to move southward causing crustal thinning within the galicia interior basin the other preferred model despite its discrepancies with gravity inversion results implies synchronous motion of the galicia bank and southeastern flemish cap until breakup between the southeastern newfoundland and iberian margins initiating 140 ma in addition to the deformation induced by the motion of the galicia bank this study demonstrates the influence of inherited variscan structures and their impact on rift segmentation experienced within the galicia interior basin this is inferred through attempts to discretize triangular meshes within regions of deformation in areas where inherited structures have been previously interpreted

the roza member columbia river basalt group a gigantic pahoehoe lava flow field formed by endogenous processes we present studies on the physical volcanology of the 15 ma roza member of the wanapum formation in the columbia river basalt group the roza member represents a compound pahoehoe flood basalt lava flow field with an area of 40 300 km 2 and a volume of 1300 km 3 it consists of 4 major lava flows each composed of numerous decimeter to kilometer long pahoehoe lobes roza lavas feature a wide range of pahoehoe surface structures such as lava rise plateaus tumuli and surface breakouts and we illustrate that the lava morphology is inconsistent with previous proposals of rapid emplacement for these lavas an integral component of the roza flow field is the sheet lobe with internal structures identical to those of inflated pahoehoe sheet lobes from hawaii and iceland both at the same scale and at much larger scales we identify a three part division of the sheet lobes into basal crust lava core and lava crust which are interpreted as the equivalent to the bottom crust the liquid lava core and the surface crust of an active inflating pahoehoe lobe the upper lava crust grows continuously during lava emplacement and its growth rate can be approximated by conductive cooling this relationship is used to calculate the emplacement time for individual roza sheet lobes and to derive a first order estimate on the duration of the roza eruption the results indicate that the emplacement of individual roza lobes lasted for months to years and that the lava flow field was constructed over a period of at least 14 years we propose that the roza flows achieved great areal dimensions and thicknesses by inflation and endogenous growth as the lava flowed from vent to flow front it traveled under an insulating crust which maintained cooling rates of 0 1 c km and allowed for efficient transport of lava over distances up to 300 km

electrically conducting ca rich brines rather than water expected in the martian subsurface 1 if mars ever possessed a salty liquid hydrosphere which later partly evaporated and froze down then any aqueous fluids left near the surface could have evolved to become dense eutectic brines eutectic brines by definition are the last to freeze and the first to melt if cacl2 rich such brines can remain liquid until temperatures below 220 k close to the average surface temperature of mars in the martian subsurface in intimate contact with the ca rich basaltic regolith nacl rich early brines should have reacted to become ca rich fractional crystallization freezing and partial melting would also drive brines toward cacl2 rich compositions in other words eutectic brine compositions could be present in the shallow subsurface of mars for the same reasons that eutectic magma compositions are common on earth don juan pond antarctica a cacl2 rich eutectic brine provides a possible terrestrial analog particularly because it is fed from a basaltic aquifer owing to their relative density and fluid nature brines in the martian regolith should eventually become sandwiched between ice above and salts beneath a thawing brine sandwich provides one explanation among many for the young gullies recently attributed to seepage of liquid water on mars whether or not brine seepage explains the gullies phenomenon dense cacl2 rich brines are to be expected in the deep subsurface of mars although they might be somewhat diluted temperatures permitting and of variable salt composition in any case they should be good conductors of electricity

long term sea level fluctuations driven by ocean basin dynamics earth9s long term sea level history is characterized by widespread continental flooding in the cretaceous period 145 to 65 million years ago followed by gradual regression of inland seas however published estimates of the late cretaceous sea level high differ by half an order of magnitude from 40 to 250 meters above the present level the low estimate is based on the stratigraphy of the new jersey margin by assimilating marine geophysical data into reconstructions of ancient ocean basins we model a late cretaceous sea level that is 170 85 to 270 meters higher than it is today we use a mantle convection model to suggest that new jersey subsided by 105 to 180 meters in the past 70 million years because of north america9s westward passage over the subducted farallon plate this mechanism reconciles new jersey margin based sea level estimates with ocean basin reconstructions

gplates building a virtual earth through deep time gplates is an open source cross platform plate tectonic geographic information system enabling the interactive manipulation of plate tectonic reconstructions and the visualization of geodata through geological time gplates allows the building of topological plate models representing the mosaic of evolving plate boundary networks through time useful for computing plate velocity fields as surface boundary conditions for mantle convection models and for investigating physical and chemical exchanges of material between the surface and the deep earth along tectonic plate boundaries the ability of gplates to visualize subsurface 3 d scalar fields together with traditional geological surface data enables researchers to analyze their relationships through geological time in a common plate tectonic reference frame to achieve this a hierarchical cube map framework is used for rendering reconstructed surface raster data to support the rendering of subsurface 3 d scalar fields using graphics hardware accelerated ray tracing techniques gplates enables the construction of plate deformation zones regions combining extension compression and shearing that accommodate the relative motion between rigid blocks users can explore how strain rates stretching shortening factors and crustal thickness evolve through space and time and interactively update the kinematics associated with deformation where data sets described by geometries points lines or polygons fall within deformation regions the deformation can be applied to these geometries together these tools allow users to build virtual earth models that quantitatively describe continental assembly fragmentation and dispersal and are interoperable with many other mapping and modeling tools enabling applications in tectonics geodynamics basin evolution orogenesis deep earth resource exploration paleobiology paleoceanography and paleoclimate

unusually cu rich magmas associated with giant porphyry copper deposits evidence from bingham utah mass balance constraints indicate that formation of giant porphyry copper deposits pcds requires either highly efficient collection of cu from large volumes of magma or unusually cu rich parent magmas support for the second of these possibilities has been discovered in the form of mafic enclaves with abundant bornite and chalcopyrite in the last chance stock one of the parent intrusions of the giant bingham pcd utah united states mineral assemblages and compositions indicate that the last chance enclaves are autoliths consisting of phases that crystallized from the intrusion and that the intrusion was unusually enriched in cu one possible mechanism for generating cu rich magmas is fractional crystallization during pyrrhotite undersaturated conditions the high fo 2 conditions observed for the last chance stock may have allowed such an evolution alternatively if the magma has not undergone significant fractionation early crystallization of chalcopyrite and bornite from the magma would indicate that the lower crustal source region for the magma probably contained cu fe sulfides possible cu rich source regions are a subcrustal mafic intrusion with sulfide cumulates or a deeply buried metamorphic terrane containing cu deposits such as those in the curaca valley brazil or okiep south africa heterogeneous distribution of cu fe sulfides in an okiep type source terrane would produce local pcds such as bingham or large accumulations of cu fe sulfides possibly in the form of cumulates in subcrustal intrusions at convergent margins could produce giant pcd provinces such as those in indonesia papua new guinea and central chile

mantle induced subsidence and compression in se asia since the early miocene rift basins developed extensively across sundaland the continental core of southeast asia since the eocene beginning in the early miocene basins in southern sundaland experienced widespread synchronous compression inversion and marine inundation despite a large drop in long term global sea level the mechanism for this large scale synchronous regional sea level rise basin inversion and subsidence is not well understood and contrary to expectations from traditional basin models and eustatic sea level trends we present geodynamic models of mantle convection with both deformable and rigid plate reconstructions to investigate this enigma models suggest that a slab stagnates within the transition zone beneath southeast asia before the miocene the stagnant slab penetrated through the 660 km mantle discontinuity during the early miocene and formed a slab avalanche event due to continuous subduction and accumulation of negatively buoyant slabs this avalanche may have induced large scale marine inundation regional compression and basin inversion across southern sundaland we argue mantle convection induced large scale basin compression in contrast to conventional plate margin induced compression this suggests mantle convection may exert a much stronger control on surface processes than previously recognized

tectonic speed limits from plate kinematic reconstructions abstract the motion of plates and continents on the planet s surface are a manifestation of long term mantle convection and plate tectonics present day plate velocities provide a snapshot of this ongoing process and have been used to infer controlling factors on the speeds of plates and continents however present day velocities do not capture plate behaviour over geologically representative periods of time to address this shortcoming we use a plate tectonic reconstruction approach to extract time dependent plate velocities and geometries from which root mean square rms velocities are computed resulting in a median rms plate speed of 4 cm yr over 200 myr linking tectonothermal ages of continental lithosphere to the rms plate velocity analysis we find that the increasing portions of plate area composed of continental and or cratonic lithosphere significantly reduces plate speeds plates with any cratonic portion have a median rms velocity of 5 8 cm yr while plates with more than 25 of cratonic area have a median rms speed of 2 8 cm yr the fastest plates 8 5 cm yr rms speed have little continental fraction and tend to be bounded by subduction zones while the slowest plates 2 6 2 8 cm yr rms speed have large continental fractions and usually have little to no subducting part of plate perimeter more generally oceanic plates tend to move 2 3 times faster than continental plates consistent with predictions of numerical models of mantle convection the slower motion of continental plates is compatible with deep keels impinging on asthenospheric flow and increasing shear traction thus anchoring the plate in the more viscous mantle transition zone we also find that short lived up to 10 myr rapid accelerations of africa 100 and 65 ma north america 100 and 55 ma and india 130 80 and 65 ma appear to be correlated with plume head arrivals as recorded by large igneous province lips emplacement by evaluating factors influencing plate speeds over the mesozoic and cenozoic our temporal analysis reveals simple principles that can guide the construction and evaluation of absolute plate motion models for times before the cretaceous in the absence of hotspot tracks and seafloor spreading histories based on the post pangea plate motions one principle that can be applied to pre pangea times is that plates with less than 50 continental area can reach rms velocities of 20 cm yr while plates with more than 50 continental fraction do not exceed rms velocities of 10 cm yr similarly plates with large portions of continental or cratonic area with rms velocities exceeding 15 cm yr for more than 10 myr should be considered as potential artefacts requiring further justification of plate driving forces in such scenarios

new age constraints for the middle triassic archosaur lotosaurus implications for basal archosaurian appearance and radiation in south china abstract archosaurians were the dominant terrestrial tetrapods during the mesozoic and became one of the most successful tetrapod clades on earth following the end permian mass extinction the lower badong formation in northwestern hunan province south china hosts fossils representing the basal archosaurian lotosaurus the badong formation has been previously interpreted as anisian ladinian 247 237 ma in age based on biostratigraphic correlations this study presents new detrital zircon u pb age constraints for sandstones hosting lotosaurus fossils in sangzhi county of northwestern hunan our data give a weighted mean age of 238 0 1 4 ma ladinian stage as the maximum depositional age for the fossil bearing layer in the lower badong formation this age is consistent with younger estimates from previous biostratigraphic studies it is also more precise and stratigraphically constrained than previously published radiometric dating results for the units this age estimate provides critical geochronologic constraint on the radiation of early archosaurians from china into other areas of pangea beginning in the early triassic

validation of tectonic reconstructions by crustal volume balance new zealand through the cenozoic we describe a procedure that allows us to quantitatively test hypotheses about the tectonic evolution of a region including areas for which there is little or no geologic record and apply it to the pacific australian plate boundary in the new zealand region since 65 ma the derived models are a first attempt to quantify the effects of the development of the modern plate boundary on four major components of the tectonic evolution of new zealand i e sedimentation paleogeography growth of crustal root and nonrigid deformation the technique balances total rock volume through time using estimates of these factors although the solutions are non unique the uncertainties in each factor can be estimated and used to define the models the plate reconstructions we present are minor modifications of earlier work developed to test whether those proposed reconstructions are self consistent and consistent with present day crustal structure and sediment distribution they are digital and geographically referenced and they have the advantage that new data can be readily incorporated and new concepts tested against several criteria the model of the evolution of new zealand9s crustal root is new and incorporates a previously unpublished compilation the models show that rock redistribution is accounted for by erosion and sedimentation during the period 65 25 ma the pacific australian plate boundary began propagating through new zealand ca 45 ma in these models development of the boundary has no effect on nonrigid deformation until ca 25 ma that time marked the start of a significant increase in land area and of the nonrigid deformation of a large region in the center of the new zealand continent since ca 20 ma 575 000 km 3 of sediments were deposited in basins around new zealand and a crustal root with a volume of 2 200 000 km 3 is interpreted to have developed beneath the landmass a large area in the center of late cretaceous and tertiary reconstructions of the new zealand region inferred from outcrop well and seismic reflection data deformed eroded and was eventually amalgamated within the continental crust of new zealand a redistribution of 3 080 000 km 3 of rock at 0 porosity

convergence of tectonic reconstructions and mantle convection models for significant fluctuations in seafloor spreading for 50 years of data collection and kinematic reconstruction efforts plate models have provided alternative scenarios for plate motions and seafloor spreading for the past 200 my however these efforts are naturally limited by the incomplete preservation of very old seafloor and therefore the time dependence of the production of new seafloor is controversial there is no consensus on how much it has varied in the past 200 my and how it could have fluctuated over longer timescales we explore how seafloor spreading and continental drift evolve over long geological periods using independently derived models a recently developed geodynamic modelling approach and state of the art plate reconstructions both kinematic reconstructions and geodynamic models converge on variations by a factor of 2 in the rate of production of new seafloor over a wilson cycle with concomitant changes of the shape of the area age distribution of the seafloor between end members of rectangular triangular and skewed distributions convection models show that significant fluctuations over longer periods 1 gy should exist involving changes in ridge length and global tectonic reorganisations although independent both convection models and kinematic reconstructions suggest that changes in ridge length are at least as significant as spreading rate fluctuations in driving changes in the seafloor area age distribution through time

middle miocene climate and vegetation models and their validation with proxy data abstract the miocene is a relatively recent epoch of the earth s history with warmer climate than today particularly during the middle miocene climatic optimum mmco approximately 17 15 ma although the cause of the warming is probably not only attributable to co2 but also to changes in orography and configuration of ocean gateways this time interval represents an ideal case study to test the ability of climate models to simulate warm climates comparable to those that the earth may experience in the near future however even with higher than present day co2 concentrations the mmco warming inferred from terrestrial proxy data has been difficult to reproduce in climate models since fossil flora do not provide direct information on climate but on flora and vegetation climate model results are generally compared to climate reconstructions obtained from the fossil flora in this study we apply an alternative method by simulating palaeovegetation from the outputs of the climate model using a dynamic vegetation model model vegetation reconstruction can then be compared to the vegetation cover indicated by the fossil flora record at the various localities provided that a common classification of plant functional types pfts is used for the data and the model here we reconstruct the vegetation of the middle miocene with the global dynamic vegetation model caraib using the climatologies derived from five atmospheric general circulation models the reliability of the simulations is examined on a presence absence basis of pfts by comparison of vegetation reconstructions to palaeoflora data recorded in the northern hemisphere and the tropics this comparison provides an overall agreement around 60 between model and data when all sites and tree types are considered three model simulations out of five show to be better at predicting the absence than the presence the presence of warm temperate mixed forests in the middle latitudes dominated by broadleaved deciduous warm temperate and subtropical trees is generally well reproduced in caraib simulations however poor agreement is obtained for the presence of tropical pfts out of the tropics and for warm pfts at latitudes northward of 50 n where climate models remain too cold to produce assemblages of trees consistent with the data nevertheless the model data comparison performed here highlights several mismatches that could result not only from missing feedbacks in the climate simulations but also from the data the results of the likelihood analysis on presence absence of pfts illustrate the uncertainties in the pft classification of the neogene floral records the coexistence of some pfts in the palaeovegetation data is impossible to reproduce in the vegetation model simulations because of the climatic definition of the modern pfts this result indicates either a bias in the identification of modern analogues for fossil plant taxa or a possible evolution of environmental requirements of certain plants

transform marginal plateaus abstract numerous submarine plateaus form highstanding bathymetric highs at continent to ocean transitions due to their proximity to continents they have been frequently labelled marginal plateaus although this term has not been clearly defined or associated with a specific geology or geodynamic process until now these elevations have been interpreted as submerged thinned continental fragments detached from continents basaltic buildups formed by hotspots volcanic margins or oceanic plateaus many of these plateaus formed at transform margins connecting oceanic basins of contrasted ages we propose for the first time to define and review a class of marginal plateaus related to a specific tectonic setting transform marginal plateaus tmps based on a compilation of 20 tmps around the world we show that most of them have a polyphased history and have undergone at least one major volcanic phase our review highlights in particular a hitherto unrecognized close link between hotspots volcanic activity and transform margins we also propose that due to their polyphased history tmps may contain several successive basins and overlooked long lived sedimentary archives we finally highlight that because these tmps were transform plate boundaries perpendicular or oblique to surrounding rifts many of them were close to last contact points during final continental breakup and may have formed land bridges or bathymetric highs between continents therefore we discuss broader scientific issues such as the interest of tmps in recording and studying the onset and variations of oceanic currents or past biodiversity growth bio connectivity and lineage evolution

evolution of a plume influenced source to sink system an example from the coupled central emeishan large igneous province and adjacent western yangtze cratonic basin in the late permian sw china abstract source to sink paleogeography in a time constrained sequence stratigraphic framework has been reconstructed for the non marine to marine transitional lopingian strata late permian in the western yangtze cratonic basin wycb and the adjacent inner zone of the emeishan large igneous province elip in order to reveal the evolution of a mantle plume influenced cratonic basin the lopingian coal bearing strata can be subdivided into seventeen 4th order sequences and three 3rd order composite sequences representing 6 76 myr paleogeographic reconstructions of the wycb demonstrate the existence of n s trending terrestrial transitional and marine facies belts distributed west to east away from the central elip geomorphological analysis indicates that the western boundary of the source area coincided with the major axis of the uplifted central elip based on sediment flux estimates and modeling bqart model relief of the central elip increased from near sea level in the earliest late permian and reached equilibrium at about 200 m in the latest permian sediment volume backfilling analysis indicates that total tectonic uplift of the central elip in the late permian was more than 500 m evolution of the coupled central elip and wycb can be subdivided into three stages pre eruptive uplift stage pre and syn eruptive subsidence stage and syn and post eruptive uplift stage post eruptive basin filling was controlled by sediment supply that was related to tectonic uplift drainage topography and climate change and basin accommodation that was related to sea level fluctuations and plume induced syn sedimentary tectonics

temperate rainforests near the south pole during peak cretaceous warmth the mid cretaceous period was one of the warmest intervals of the past 140 million years1 5 driven by atmospheric carbon dioxide levels of around 1 000 parts per million by volume6 in the near absence of proximal geological records from south of the antarctic circle it is disputed whether polar ice could exist under such environmental conditions here we use a sedimentary sequence recovered from the west antarctic shelf the southernmost cretaceous record reported so far and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82 s during the turonian santonian age 92 to 83 million years ago this record contains an intact 3 metre long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores a climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1 120 1 680 parts per million by volume and a vegetated land surface without major antarctic glaciation highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide multi proxy core data and model simulations support the presence of temperate rainforests near the south pole during mid cretaceous warmth indicating very high co2 levels and the absence of antarctic ice

subduction controls the distribution and fragmentation of earth s tectonic plates the theory of plate tectonics describes how the surface of the earth is split into an organized jigsaw of seven large plates 1 of similar sizes and a population of smaller plates whose areas follow a fractal distribution 2 3 the reconstruction of global tectonics during the past 200 my 4 suggests that this layout is probably a long term feature of our planet but the forces governing it are unknown previous studies 3 5 6 primarily based on statistical properties of plate distributions were unable to resolve how the size of plates is determined by lithosphere properties and or underlying mantle convection here we demonstrate that the plate layout of the earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere using 3d spherical models of mantle convection with plate like behaviour that match the plate size frequency distribution observed for earth we show that subduction geometry drives the tectonic fragmentation that generates plates the spacing between slabs controls the layout of large plates and the stresses caused by the bending of trenches break plates into smaller fragments our results explain why the fast evolution in small back arc plates 7 8 reflects the dramatic changes in plate motions during times of major reorganizations our study opens the way to use convection simulations with plate like behaviour to unravel how global tectonics and mantle convection are dynamically connected

dynamic topography and eustasy controlled the paleogeographic evolution of northern africa since the mid cretaceous northern africa underwent widespread inundation during the late cretaceous changes in eustasy do not explain the absence of this inundation across the remainder of africa and the timing and location of documented tectonic deformation do not explain the large scale paleogeographic evolution we investigate the combined effects of vertical surface displacements predicted by a series of mantle flow models and eustasy on northern african paleoenvironmental change we compare changes in base level computed as the difference between eustasy and long wavelength dynamic topography arising from sources of buoyancy deeper than 350 km to the evolution of paleoshorelines derived from two interpolated global data sets since the mid cretaceous we also compare the predicted mantle temperature field of these mantle flow models at present day to several seismic tomography models this approach reveals that dynamic subsidence related to africa s northward motion away from the buoyant regions overlying the african large low shear velocity province amplified sea level rise resulting in maximum inundation of northern africa during the cenomanian and turonian by the cenozoic decreased magnitudes of dynamic subsidence reflecting the reduced drawdown effects of slab material beneath northern africa associated with the impact of the africa eurasia collision combined with a comparatively pronounced progressive sea level fall resulted in ongoing region wide regression along coastal regions the temporal match between our preferred model and the paleoshoreline data sets suggests that the paleogeographic evolution of this region since the late cretaceous has mainly been influenced by the interplay between eustasy and long wavelength dynamic topography arising from large scale subduction driven lower mantle convection

ocean basin evolution and global scale plate reorganization events since pangea breakup we present a revised global plate motion model with continuously closing plate boundaries ranging from the triassic at 230 ma to the present day assess differences among alternative absolute plate motion models and review global tectonic events relatively high mean absolute plate motion rates of approximately 9 10 cm yr 1 between 140 and 120 ma may be related to transient plate motion accelerations driven by the successive emplacement of a sequence of large igneous provinces during that time an event at 100 ma is most clearly expressed in the indian ocean and may reflect the initiation of andean style subduction along southern continental eurasia whereas an acceleration at 80 ma of mean rates from 6 to 8 cm yr 1 reflects the initial northward acceleration of india and simultaneous speedups of plates in the pacific an event at 50 ma expressed in relative and some absolute plate motion changes around the globe and in a reduction of global mean plate speeds from about 6 to 4 5 cm yr 1 indicates that an increase in collisional forces such as the india eurasia collision and ridge subduction events in the pacific such as the izanagi pacific ridge play a significant role in modulating plate velocities

dynamic topography of passive continental margins and their hinterlands since the cretaceous abstract even though it is well accepted that the earth s surface topography has been affected by mantle convection induced dynamic topography its magnitude and time dependence remain controversial the dynamic influence to topographic change along continental margins is particularly difficult to unravel because their stratigraphic record is dominated by tectonic subsidence caused by rifting we follow a three fold approach to estimate dynamic topographic change along passive margins based on a set of seven global mantle convection models we first demonstrate that a geodynamic forward model that includes adiabatic and viscous heating in addition to internal heating from radiogenic sources and a mantle viscosity profile with a gradual increase in viscosity below the mantle transition zone provides a greatly improved match to the spectral range of residual topography end members as compared with previous models at very long wavelengths spherical degrees 2 3 we then combine global sea level estimates with predicted surface dynamic topography to evaluate the match between predicted continental flooding patterns and published paleo coastlines by comparing predicted versus geologically reconstructed land fractions and spatial overlaps of flooded regions for individual continents since 140 ma modelled versus geologically reconstructed land fractions match within 10 for most models and the spatial overlaps of inundated regions are mostly between 85 and 100 for the cenozoic dropping to about 75 100 in the cretaceous regions that have been strongly affected by mantle plumes are generally not captured well in our models as plumes are suppressed in most of them and our models with dynamically evolving plumes do not replicate the location and timing of observed plume products we categorise the evolution of modelled dynamic topography in both continental interiors and along passive margins using cluster analysis to investigate how clusters of similar dynamic topography time series are distributed spatially a subdivision of four clusters is found to best reveal end members of dynamic topography evolution along passive margins and their hinterlands differentiating topographic stability long term pronounced subsidence initial stability over a dynamic high followed by moderate subsidence and regions that are relatively proximal to subduction zones with varied dynamic topography histories along passive continental margins the most commonly observed process is a gradual motion from dynamic highs towards lows during the fragmentation of pangea reflecting the location of many passive margins now over slabs sinking in the lower mantle our best fit model results in up to 500 150 m of total dynamic subsidence of continental interiors while along passive margins the maximum predicted dynamic topographic change over 140 million years is about 350 150 m of subsidence models with plumes exhibit clusters of transient passive margin uplift of about 200 200 m but are mainly characterised by long term subsidence of up to 400 m the good overall match between predicted dynamic topography to geologically mapped paleo coastlines makes a convincing case that mantle driven topographic change is a critical component of relative sea level change and indeed the main driving force for generating the observed geometries and timings of large scale continental inundation through time

organization of the tectonic plates in the last 200 myr the present tessellation of the earth s surface into tectonic plates displays a remarkably regular plate size distribution described by either one sornette and pisarenko 2003 or two bird 2003 statistically distinct groups characterised by large and small plate size a unique distribution implies a hierarchical structure from the largest to the smallest plate alternatively two distributions indicate distinct evolutionary laws for large and small plates the first tied to mantle flow the second determined by a hierarchical fragmentation process we analyse detailed reconstructions of plate boundaries during the last 200 myr and find that i large and small plates display distinct statistical distributions ii the small plates display little organisational change since 60 ma and iii the large plates oscillate between heterogeneous 200 170 myr and 65 50 ma and homogeneous 120 100 ma plate tessellations on a timescale of about 100 myr heterogeneous states are reached more rapidly while the plate configuration decays into homogeneous states following a slower asymptotic curve suggesting that heterogeneous configurations are excited states while homogeneous tessellations are equilibrium states we explain this evolution by proposing a model that alternates between bottom and top driven earth dynamics physically described by fluid dynamic analogies the rayleigh benard and benard marangoni convection respectively we discuss the implications for true polar wander tpw global kinematic reorganisations 50 and 100 ma and the earth s magnetic field inversion frequency

oceanic plateau of the hawaiian mantle plume head subducted to the uppermost lower mantle the hawaiian emperor seamount chain that includes the hawaiian volcanoes was created by the hawaiian mantle plume although the mantle plume hypothesis predicts an oceanic plateau produced by massive decompression melting during the initiation stage of the hawaiian hot spot the fate of this plateau is unclear we discovered a megameter scale portion of thickened oceanic crust in the uppermost lower mantle west of the sea of okhotsk by stacking seismic waveforms of ss precursors we propose that this thick crust represents a major part of the oceanic plateau that was created by the hawaiian plume head 100 million years ago and subducted 20 million to 30 million years ago our discovery provides temporal and spatial clues of the early history of the hawaiian plume for future plate reconstructions

a dynamic process for drowning carbonate reefs on the northeastern australian margin drowned carbonate reefs on passive margins are puzzling because of their enormous growth potential compared to typical rates of passive margin subsidence and moderate sea level fluctuations a possible solution to this paradox is that slow processes acting over geologic time weaken reefs and contribute to their ultimate demise the australian northeastern marginal plateaus known for their drowned reefs underwent a period of accelerated tectonic subsidence during the late miocene to pliocene that combined with a sequence of second order global sea level rises outpaced reef growth and drowned the once thriving miocene carbonate platforms however the mechanism for the observed anomalous subsidence of this relatively mature passive margin 1000 km from the nearest plate boundary is uncertain we use a coupled plate kinematic mantle flow model to show that in the late miocene northeastern australia overrode subducted slabs from eocene melanesian subduction north of papua new guinea we find that the rate of surface subsidence induced by the sinking slabs increases the likelihood that relative sea level rises outpaced late miocene reef growth in addition to the well known effects of long term plate processes and short term global sea level and climate change our results demonstrate that deep earth processes can play a substantial role in driving the evolution of passive margins and coral reefs

coupled southern ocean cooling and antarctic ice sheet expansion during the middle miocene the middle miocene climate transition 14 million years ago was characterized by a dramatic increase in the volume of the antarctic ice sheet the driving mechanism of this transition remains under discussion with hypotheses including circulation changes declining carbon dioxide in the atmosphere and orbital forcing southern ocean records of planktic foraminiferal mg ca have previously been interpreted to indicate a cooling of 6 7 c and a decrease in salinity that preceded antarctic cryosphere expansion by up to 300 000 years this interpretation has led to the hypothesis that changes in meridional heat and vapour transport along with an early thermal isolation of antarctica from extrapolar climates played a fundamental role in triggering ice growth here we revisit the middle miocene southern ocean temperature evolution using clumped isotope and lipid biomarker temperature proxies our records indicate that the southern ocean cooling and the associated salinity decrease occurred in phase with the expansion of the antarctic ice sheet we demonstrate that the timing and magnitude of the southern ocean temperature change seen in previous reconstructions can be explained if we consider ph as an additional non thermal control on foraminiferal mg ca ratios therefore our new dataset challenges the view of a thermal isolation of antarctica preceding ice sheet expansion and suggests a strong coupling between southern ocean conditions and antarctic ice volume in times of declining atmospheric carbon dioxide antarctic ice volume expansion in the middle miocene coincides with southern ocean cooling according to biomarker and clumped isotope temperature records from south of tasmania

a compilation of igneous rock volumes at volcanic passive continental margins from interpreted seismic profiles abstract the rifting and breakup of continents and subsequent seafloor spreading give rise to passive continental margins many of which are underlain by enormous volumes of igneous rocks and termed volcanic passive margins the relationships between the igneous rocks rifting and mantle plumes remain unresolved despite extensive studies and proposed alternative models to support such studies we use published previously interpreted seismic reflection and refraction data to compile a dataset of igneous rock volumes and geometries at volcanic passive continental margins the volmir volcanic passive margin igneous rocks dataset is based on margin crossing profiles on which the volumes and geometries of both shallow seaward dipping reflector sdr and deeper high velocity lower crustal hvlc units can be measured it includes information about the ages of continental breakup and profile distances from the associated euler pole and from hotspots that may have played roles in the breakup process despite local variations the dataset shows general patterns the average ratio of sdr to hvlc volumes 0 3 0 4 is relatively consistent between profiles implying that formation of these units is related during continental breakup the volumes of igneous rocks display a moderate positive correlation with distances from the euler pole but only a weak negative correlation with distances from the nearest hotspot at the time of margin formation suggesting that in continental breakup lithospheric processes passive rifting have greater effects than hotspots active rifting these results suggest that this dataset will be useful for exploring aspects of the rifting process relationships between volcanic rifted margins and potential explanations for their similarities and differences

the tectonic fabric of the ocean basins 1 we present a global community data set of fracture zones fzs discordant zones propagating ridges v shaped structures and extinct ridges digitized from vertical gravity gradient vgg maps we use a new semi automatic fz tracking program to test the precision of our hand digitized traces and find a mean absolute deviation of less than 3 4 km from the raw vgg minima that most clearly delineate each feature and less than 5 4 km from the fz location predicted by fitting model profiles to the vgg data that represent the morphology of the individual fzs these offsets are small considering gravity data only provide an approximation for the underlying basement morphology we further investigate the origin of non fz seafloor fabric by combining published abyssal hill heights computed from gravity anomalies with global half spreading rates a residual abyssal hill height grid with spreading rate effects removed combined with our interpreted tectonic fabric reveals several types of seafloor fabric distinct from typical abyssal hills where discordant zones do not overprint abyssal hill signals residual abyssal hill height anomalies correspond to seafloor that accreted near mantle thermal anomalies or zones of melt depletion our analysis reveals several areas where residual abyssal hill height anomalies reflect pseudo faults and extinct ridges associated with ridge propagation and or microplate formation in the southern pacific ocean

burma terrane part of the trans tethyan arc during collision with india according to palaeomagnetic data convergence between the indian and asian plates has reshaped large parts of asia changing regional climate and biodiversity yet geodynamic models fundamentally diverge on how convergence was accommodated since the india asia collision here we report paleomagnetic data from the burma terrane at the eastern edge of the collision zone and famous for its cretaceous amber biota to better determine the evolution of the india asia collision the burma terrane was part of a trans tethyan island arc and stood at a near equatorial southern latitude at 95 ma suggesting island endemism for the burmese amber biota the burma terrane underwent significant clockwise rotation between 80 50 ma causing its subduction margin to become hyper oblique subsequently it was translated northward on the indian plate by an exceptional distance of at least 2000 km along a dextral strike slip fault system in the east our reconstructions are only compatible with geodynamic models involving a first collision of india with a near equatorial trans tethyan subduction system at 60 ma followed by a later collision with the asian margin

paleozoic crustal blocks of onshore and offshore central argentina new pieces of the southwestern gondwana collage and their role in the accretion of patagonia and the evolution of mesozoic south atlantic sedimentary basins abstract the southwestern gondwana basement block configuration in the central argentinean offshore area was analyzed using gravimetric magnetic and seismic data and existing onshore tectonic models the resultant maps the distribution of the mesozoic and cenozoic basins and paleozoic structural features were used to validate the interpretations and to produce a new regional tectonic model pre carboniferous southwestern gondwana of south america was interpreted as an open margin formed from east to west by the dom feliciano belt the rio de la plata craton the pampean belt and the pampia and cuyania terranes the collision of the patagonia allochthonous terrane during the late paleozoic resulted in the development of the ventania cape fold belt which was mapped for the first time off the argentinean coast out to 600 km from the shore a strong change in the orientation of the fold belt is referred to as the colorado syntaxis a mirror image of the cape syntaxis in south africa this change reflects the buttressing effect of the cratonic blocks that hamper the northward propagation of syncollisional deformation and resulted in a 180 km shift of the orogenic front the mesozoic basins and the basement block distribution were analyzed the pampean belt a deformed area produced by the pampia accretion to the cratonic area is the locus to two episutural basins the general levalle and macachin basins the salado basin was interpreted as an episutural basin controlled by a 2 1 2 0 ga suture within the rio de la plata craton the colorado basin is composed of four segmented depocenters that reflect different emplacement controls the location of the western colorado basin was controlled by the upper paleozoic orogen the distributions of the central and eastern colorado depocenters orthogonal to the continental boundary were also strongly influenced by the upper paleozoic structures and were offset by lineaments that reflect dom feliciano fabric the colorado basin external depocenter that parallels the continental margin was also controlled by these lineaments we interpret a time gap of some 50 ma between the beginning of the evolution of the margin orthogonal depocenters and the atlantic breakup

eocene 46 44 ma onset of australia pacific plate motion in the southwest pacific inferred from stratigraphy in new caledonia and new zealand

convection of north pacific deep water during the early cenozoic the history of deep water formation and abyssal flow is poorly known but important to establish in order to develop a better understanding of changes in oceanic mass heat salt and nutrient transport north atlantic high latitude regions currently are the dominant deep water producers but paleogeographic constraints proxy interpretations and physical models have suggested other modes for the past such as those characterized by high latitude pacific sources subtropical sources or widespread nonlocalized sources here we present new north pacific late cretaceous paleogene nd isotope data from fossil fish debris and detrital silicates combined with results of coupled climate model simulations to test these hypothesized circulation modes the data and model simulations support a circulation mode characterized by high latitude bipolar pacific convection deep convection in the north pacific and likely the south pacific was most intense during the relatively cool portion of the late cretaceous paleocene and waned prior to the peak global warmth of the early eocene ca 52 ma

full fit palinspastic reconstruction of the conjugate australian antarctic margins 1 despite decades of study the prerift configuration and early rifting history between australia and antarctica is not well established the plate boundary system during the cretaceous includes the evolving kerguelen broken ridge large igneous province in the west as well as the conjugate passive and transform margin segments of the australian and antarctic continents previous rigid plate reconstruction models have highlighted the difficulty in satisfying all the available observations within a single coherent reconstruction history we investigate a range of scenarios for the early rifting history of these plates by developing a deforming plate model for this conjugate margin pair potential field data are used to define the boundaries of stretched continental crust on a regional scale integrating crustal thickness along tectonic flow lines provides an estimate of the prerift location of the continental plate boundary we then use the prerift plate boundary positions along with additional constraints from geological structures and large igneous provinces within the same australian and antarctic plate system to compute full fit poles of rotation for australia relative to antarctica our preferred model implies that the leeuwin and vincennes fracture zones are conjugate features within gondwana but that the direction of initial opening between australia and antarctica does not follow the orientation of these features rather the geometry of these features is likely related to the earlier rifting of india away from australia antarctica previous full fit reconstructions based on qualitative estimates of continental margin overlaps generally yield a tighter fit than our preferred reconstruction based on palinspastic margin restoration

emag2 a 2 arc min resolution earth magnetic anomaly grid compiled from satellite airborne and marine magnetic measurements 1 a global earth magnetic anomaly grid emag2 has been compiled from satellite ship and airborne magnetic measurements emag2 is a significant update of our previous candidate grid for the world digital magnetic anomaly map the resolution has been improved from 3 arc min to 2 arc min and the altitude has been reduced from 5 km to 4 km above the geoid additional grid and track line data have been included both over land and the oceans wherever available the original shipborne and airborne data were used instead of precompiled oceanic magnetic grids interpolation between sparse track lines in the oceans was improved by directional gridding and extrapolation based on an oceanic crustal age model the longest wavelengths 330 km were replaced with the latest champ satellite magnetic field model mf6 emag2 is available at http geomag org models emag2 and for permanent archive at http earthref org cgi bin er cgi s erda cgi n 970

abrupt plate accelerations shape rifted continental margins rifted margins are formed by persistent stretching of continental lithosphere until breakup is achieved it is well known that strain rate dependent processes control rift evolution yet quantified extension histories of earth s major passive margins have become available only recently here we investigate rift kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions we find that rifted margins feature an initial slow rift phase less than ten millimetres per year full rate and that an abrupt increase of plate divergence introduces a fast rift phase plate acceleration takes place before continental rupture and considerable margin area is created during each phase we reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions the extension models suggest that the two phase velocity behaviour is caused by a rift intrinsic strength velocity feedback which can be robustly inferred for diverse lithosphere configurations and rheologies our results explain differences between proximal and distal margin areas and demonstrate that abrupt plate acceleration during continental rifting is controlled by the nonlinear decay of the resistive rift strength force this mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes offering new insights into the balance of plate driving forces through time

a polar dinosaur feather assemblage from australia abstract exceptionally preserved mesozoic feathered dinosaur fossils including birds are famous but recognized from only very few localities worldwide and are especially rare in the southern hemisphere here we report an assemblage of non avian and avian dinosaur feathers from an early cretaceous polar around 70 s environment in what is now southeastern australia the recovered remains incorporate small 10 30 mm long basal paravian like tufted body feathers open vaned contour feathers and asymmetrical bird like wing feathers that possess high angled barbs with possible remnants of barbicels amongst the geologically oldest observed to date such morphological diversity augments scant skeletal evidence for a range of insulated non avian theropods and birds inhabiting extreme southern high latitude settings during the mesozoic although some of these fossil feathers exhibit what may be residual patterning most are uniformly toned and preserve rod shaped microbodies as well as densely packed microbody imprints on the barbules that are structurally consistent with eumelanosomes geochemical analysis detected no identifiable residual biomolecules which we suspect were lost via hydrolysis and oxidization during diagenesis and weathering nevertheless an originally dark pigmentation can be reasonably inferred from these melanic traces which like the coloured feathers of modern birds might have facilitated crypsis visual communication and or thermoregulation in a cold polar habitat

constraining absolute plate motions since the triassic the absolute motion of tectonic plates since pangea can be derived from observations of hotspot trails paleomagnetism or seismic tomography however fitting observations is typically carried out in isolation without consideration for the fit to unused data or whether the resulting plate motions are geodynamically plausible through the joint evaluation of global hotspot track observations for times 80 ma first order estimates of net lithospheric rotation nlr and parameter estimation for paleo trench migration tm we present a suite of geodynamically consistent data optimized global absolute reference frames from 220 ma to the present each absolute plate motion apm model was evaluated against six published apm models together incorporating the full range of primary data constraints model performance for published and new models was quantified through a standard statistical analyses using three key diagnostic global metrics root mean square plate velocities nlr characteristics and tm behavior additionally models were assessed for consistency with published global paleomagnetic data and for ages 80 ma for predicted relative hotspot motion track geometry and time dependence optimized apm models demonstrated significantly improved global fit with geological and geophysical observations while performing consistently with geodynamic constraints critically apm models derived by limiting average rates of nlr to 0 05 myr and absolute tm velocities to 27 mm year fit geological observations including hotspot tracks this suggests that this range of nlr and tm estimates may be appropriate for earth over the last 220 myr providing a key step toward the practical integration of numerical geodynamics into plate tectonic reconstructions

heat flow in southern australia and connections with east antarctica viscosity and melt generation at the base of ice sheets are critically dependent upon heat flow yet subglacial heat flow is poorly constrained due to the logistical challenges of obtaining boreholes that intersect the bedrock beneath thick ice cover currently continental estimates of antarctic heat flow are derived from geophysical methods that provide ambiguous constraints of crustal heat sources despite their demonstrated importance for accurate predictions of future ice sheet behavior this study pursues an alternative approach by using heat flow measurements from rock units in the coompana province of southern australia which represent the geological counterparts of those beneath wilkes land in east antarctica we present nine new surface heat flow estimates from this previously uncharacterized region ranging from 40 to 70 mw m2 with an average of 57 3 mw m2 these values compare favorably to recent geophysically derived estimates of 50 75 mw m2 for the totten glacier catchment of east antarctica and to the single in situ measurement of 75 mw m2 from the law dome deep ice borehole however they are appreciably lower than the range of 56 120 mw m2 83 13 mw m2 average for the abnormally enriched proterozoic terranes of the central australian heat flow province this study provides the first regional heat flow map of geological provinces formerly contiguous with east antarctica through the application of continent scale heat flow data sets tied to a jurassic plate tectonic reconstruction for gondwana our approach reveals several discrepancies with current heat flow models derived from geophysical methods and provides a more robust analysis of subglacial heat flow using this plate tectonic synthesis as a proxy for east antarctica

large fluctuations of shallow seas in low lying southeast asia driven by mantle flow the sundaland continental promontory as the core of southeast asia is one of the lowest lying continental regions with half of the continental area presently inundated by a shallow sea the role of mantle convection in driving long wavelength topography and vertical motion of the lithosphere in this region has often been ignored when interpreting regional stratigraphy including a widespread late cretaceous eocene unconformity despite a consensus that southeast asia is presently situated over a large amplitude dynamic topography low resulting from long term post pangea subduction we use forward numerical models to link mantle flow with surface tectonics and compare predicted trends of dynamic topography with eustasy and regional paleogeography to determine the influence of mantle convection on regional basin histories a late cretaceous collision of gondwana derived terranes with sundaland choked the active margin leading to slab breakoff and a 10 15 myr long subduction hiatus slab breakoff likely resulted in several hundred meters of dynamic uplift and emergence of sundaland between 80 and 60 ma and may explain the absence of a late cretaceous eocene sedimentary record renewed subduction from 60 ma reinitiated dynamic subsidence of sundaland leading to submergence from 40 ma despite falling long term global sea levels our results highlight a complete down up down dynamic topography cycle experienced by sundaland with transient dynamic topography manifesting as a major regional unconformity in sedimentary basins

fifty years of the wilson cycle concept in plate tectonics an overview it is now more than 50 years since tuzo wilson published his paper asking did the atlantic close and then re open this led to the wilson cycle concept in which the repeated opening and closing of ocean basins along old orogenic belts is a key process in the assembly and breakup of supercontinents this implied that the processes of rifting and mountain building somehow pre conditioned and weakened the lithosphere in these regions making them susceptible to strain localization during future deformation episodes here we provide a retrospective look at the development of the concept how it has evolved over the past five decades current thinking and future focus areas the wilson cycle has proved enormously important to the theory and practice of geology and underlies much of what we know about the geological evolution of the earth and its lithosphere the concept will no doubt continue to be developed as we gain more understanding of the physical processes that control mantle convection and plate tectonics and as more data become available from currently less accessible regions

dynamic palaeogeographic reconstructions of the wuchiapingian stage lopingian late permian for the south china block abstract as an important tool in natural resource exploration palaeogeography provides a portrayal of deep time earth the south china block located in the eastern palaeotethys includes multiple natural resources e g coal shale gas bauxite etc in the permian which are well known for their important economic significance in this paper data gathered from literature amount to 431 stratigraphic sections of wuchiapingian age from south china these data were quantitatively analyzed and dynamically reconstructed in the global context under the revised plate motion model by gplates software for the first time a schematic 3 d model was constructed based on the high resolution reconstructions in this paper showing two relatively large highlands developed in the south china block during the wuchiapingian including the kangdian highland in the west and the cathaysia highland in the east and a small yunkai highland in the south a broad platform dominated depositional system with small uplifts and depressions was developed between these two highlands these reconstructions show great potential to explore enriched coal seams and shale gas in the peripheral areas of the two ancient highlands in the west and east of the south china block based on the dynamic evolution of this depositional system south china experienced an overall sea level rise with frequent secondary transgressions and regressions during the wuchiapingian this is in contrast to the widespread continental and evaporite deposits on much of pangea and its surrounding margins after the end guadalupian global regression compilation of conodont biostratigraphic data suggest that the temporal and spatial constraints on the unconformity across the guadalupian lopingian boundary glb resulted from dongwu uplift movement the regression began during the jinogondolella shannoni zone and ended in the clarkina leveni zone but the response time varies in different localities of south china these results provide detailed information about sea level eustacy tectonic uplift sedimentary hiatus resource accumulation and palaeoclimate change from the south china block during the wuchiapingian

lower mantle structure from paleogeographically constrained dynamic earth models seismic tomography reveals two large low shear velocity provinces llsvps beneath africa and the pacific ocean these structures may have existed for several 100 myr and are likely compositionally distinct based on observed seismic characteristics interpreted in light of geodynamic models and mineral physics constraints we investigate the dynamics of the llsvps through the use of evolutionary models of thermochemical convection from 250 ma to present day we use a spherical convection model in which the anomalous structures have a high bulk modulus consistent with seismic interpretation a new progressive assimilation method incorporates constraints from paleogeography using a refined plate history model with 1 myr time spacing to guide the thermal structure of the lithosphere and steer the thermal evolution of slabs in the uppermost mantle the thermochemical structures deform and migrate along the core mantle boundary cmb through coupling to plate motions and in response to slab stresses the models produce a ridge like anomaly beneath africa and a rounded pile beneath the pacific ocean which at present day agrees with tomography waveform modeling and other geodynamic studies plumes emanate from the margins of the domes and ridges of thickened boundary layer between the domes dense and viscous slabs can undermine the stability of high bulk modulus structures at the cmb high bulk modulus structures are not necessarily required to satisfy dynamic constraints on the llsvps

predicting sediment thickness on vanished ocean crust since 200 ma tracing sedimentation through time on existing and vanished seafloor is imperative for constraining long term eustasy and for calculating volumes of subducted deep sea sediments that contribute to global geochemical cycles we present regression algorithms that incorporate the age of the ocean crust and the mean distance to the nearest passive margin to predict sediment thicknesses and long term decompacted sedimentation rates since 200 ma the mean sediment thickness decreases from 220 m at 200 ma to a minimum of 140 m at 130 ma reflecting the replacement of old panthalassic ocean floor with young sediment poor mid ocean ridges followed by an increase to 365 m at present day this increase reflects the accumulation of sediments on ageing abyssal plains proximal to passive margins coupled with a decrease in the mean distance of any parcel of ocean crust to the nearest passive margin by over 700 km and a doubling of the total passive margin length at present day mean long term sedimentation rates increase from 0 5 cm ky at 160 ma to over 0 8 cm ky today caused by enhanced terrigenous sediment influx along lengthened passive margins superimposed by the onset of ocean wide carbonate sedimentation our predictive algorithms coupled to a plate tectonic model provide a framework for constraining the seafloor sediment driven eustatic sea level component which has grown from 80 to 210 m since 120 ma this implies a long term sea level rise component of 130 m partly counteracting the contemporaneous increase in ocean basin depth due to progressive crustal ageing

influence of mantle flow on the drainage of eastern australia since the jurassic period recent studies of the past eastern australian landscape from present day longitudinal river profiles and from mantle flow models suggest that the interaction of plate motion with mantle convection accounts for the two phases of large scale uplift of the region since 120 ma we coupled the dynamic topography predicted from one of these mantle flow models to a surface process model to study the evolution of the eastern australian landscape since the jurassic period we varied the rainfall regime erodibility sea level variations dynamic topography magnitude and elastic thickness across a series of experiments the approach accounts for erosion and sedimentation and simulates catchment dynamics despite the relative simplicity of our model the results provide insights on the fundamental links between dynamic topography and continental scale drainage evolution based on temporal and spatial changes in longitudinal river profiles as well as erosion and deposition maps we show that the motion of the australian plate over the convecting mantle has resulted in significant reorganization of the eastern australian drainage the model predicts that the murray river drained eastward between 150 and 120 ma and switched to westward draining due to the tilting of the australian plate from 120 ma first order comparisons of eight modeled river profiles and of the catchment shape of modeled murray darling basin are in agreement with present day observations the predicted denudation of the eastern highlands is compatible with thermochronology data and sedimentation rates along the southern australian margin are consistent with cumulative sediment thickness

modeling the miocene climatic optimum ocean circulation 1 ocean circulation is investigated using the community climate system model 3 ccsm3 forced with early to middle miocene 20 14 ma topography bathymetry vegetation and modern co2 significant bottom water formation is modeled in the weddell sea along with intermediate north component water formation in the north atlantic this is attributed primarily to stronger and weaker than modern convective preconditioning in the weddell and labrador seas respectively global meridional overturning and gyre circulation is weaker in the miocene due to weaker midlatitude westerlies in the southern hemisphere caused by lowering of the meridional surface temperature gradient in addition to regional influences on convection subsurface temperatures in the miocene are significantly higher in the far north atlantic greenland norwegian seas and arctic basin compared to the present ocean heat transport is symmetrical about the equator and resembles that simulated for late cretaceous and early cenozoic climates suggesting the northern hemisphere dominated ocean heat transport active today developed after the middle miocene simulated deep water warming in the miocene is more than an order of magnitude lower than indicated by proxies this discrepancy is not reconciled by higher co2 due to the persistence of sea ice at sites of deep water formation this suggests that either the ccsm3 is insufficiently sensitive to miocene boundary conditions greater greenhouse forcing existed than is currently reconstructed or that proxy records of warming are exaggerated given the diversity of global miocene proxy records and their near unanimous estimate of a significantly warmer earth the first two options are more likely

global plate motion frames toward a unified model 1 plate tectonics constitutes our primary framework for understanding how the earth works over geological timescales high resolution mapping of relative plate motions based on marine geophysical data has followed the discovery of geomagnetic reversals mid ocean ridges transform faults and seafloor spreading cementing the plate tectonic paradigm however so called absolute plate motions describing how the fragments of the outer shell of the earth have moved relative to a reference system such as the earth s mantle are still poorly understood accurate absolute plate motion models are essential surface boundary conditions for mantle convection models as well as for understanding past ocean circulation and climate as continent ocean distributions change with time a fundamental problem with deciphering absolute plate motions is that the earth s rotation axis and the averaged magnetic dipole axis are not necessarily fixed to the mantle reference system absolute plate motion models based on volcanic hot spot tracks are largely confined to the last 130 ma and ideally would require knowledge about the motions within the convecting mantle in contrast models based on paleomagnetic data reflect plate motion relative to the magnetic dipole axis for most of earth s history but cannot provide paleolongitudes because of the axial symmetry of the earth s magnetic dipole field we analyze four different reference frames paleomagnetic african fixed hot spot african moving hot spot and global moving hot spot discuss their uncertainties and develop a unifying approach for connecting a hot spot track system and a paleomagnetic absolute plate reference system into a hybrid model for the time period from the assembly of pangea 320 ma to the present for the last 100 ma we use a moving hot spot reference frame that takes mantle convection into account and we connect this to a pre 100 ma global paleomagnetic frame adjusted 5 in longitude to smooth the reference frame transition using plate driving force arguments and the mapping of reconstructed large igneous provinces to core mantle boundary topography we argue that continental paleolongitudes can be constrained with reasonable confidence

modeling the miocene climatic optimum part i land and atmosphere abstractthis study presents results from the community climate system model 3 ccsm3 forced with early to middle miocene 20 14 ma vegetation topography bathymetry and modern co2 a decrease in the meridional temperature gradient of 6 5 c and an increase in global mean temperature of 1 5 c are modeled in comparison with a control simulation forced with modern boundary conditions seasonal poleward displacements of the subtropical jet streams and storm tracks compared to the control simulation are associated with changes in hadley circulation and significant cooling of the polar stratosphere consistent with previously predicted effects of global warming energy budget calculations indicate that reduced albedo and topography were responsible for miocene warmth in the high latitude northern hemisphere while a combination of increased ocean heat transport and reduced albedo was responsible for relative warmth in the high latitude southern hemisphere compared to the present model data analysis suggest

symmetry of the south china sea conjugate margins in a rifting drifting and collision context abstract the symmetry of conjugate rifted margins is a first order observable feature reflecting the geodynamic processes acting during and after continental rifting the symmetry of the south china sea scs rifted margins can be deduced from comprehensive geophysical datasets on a continental margin scale here we combine three key approaches 1 lateral fault distributions are delineated according to free air gravity anomalies 2 crustal stretching styles are mapped based on gravity inversion constrained by deep seismic profiles and 3 total extension of conjugate margins is estimated according to margin restorations and tectonic settings we infer a predominantly symmetric rifting style caused by pure shear extension with only narrow domains of asymmetric deformation in continent ocean transition cot regions that have undergone simple shear and where the lower crust of the highly thinned distal margin is embrittled before continental breakup however our analysis also suggests that this symmetry has been modified by post rift geodynamic processes southward lower crustal flow which occurred only on the southern margin due to the low viscosity of the lower crust and the slab pull induced by the subducting proto scs plate during seafloor spreading shifted the crustal stretching styles from symmetric to asymmetric the collision between the southern margin and borneo thickened the lower crust more than the upper crust at the southern end of the southern margin and shortened the southern margin this event had a large impact on the se margin but a small impact on the sw margin we conclude that 1 for the se and ne margins the crustal stretching styles shifted from asymmetric to approximately symmetric and the total extension shifted from symmetric to asymmetric 2 for the sw and nw margins the crustal stretching and total extension remained asymmetric and symmetric respectively

amazonian geologic history of the echus chasma and kasei valles system on mars new data and interpretations abstract new high resolution datasets have prompted a mapping based study of the 2500 km long echus chasma and kasei valles system that utilizes geomorphic details stratigraphic relations and cratering statistics derived from the new datasets our results suggest that between the hesperian and amazonian epochs on mars 3 7 ga to recent the study area was affected by at least 4 episodes of widespread volcanic activity and 4 periods of episodic fluvio glacial activity this paper discusses the amazonian

the uncertainties of finite rotations in plate tectonics incomplete knowledge of the pattern of magnetic lineations and fossil transform faults represented by sea floor spreading data on two plates generated by the same spreading center leads to uncertainties in a reconstruction of the past relative configuration of the plates a reconstruction may be represented by the finite rotation that describes one configuration relative to another in this paper a method of reconstruction is provided that reflects the uncertainties in the data the method minimizes a weighted least squares measure of fit as a function of the rotation parameters for a given rotation the measure of fit represents the sum of squares of the weighted distances of fixed and rotated data points representing corresponding former plate margin segments from a common plate margin the common margin is estimated from the locations of both fixed and rotated data points the estimated margin consists of a set of great circle arcs it is shown how the method of reconstruction may be utilized to obtain an uncertainty region for the pole and angle of rotation that characterize the finite rotation these techniques are then used to study the uncertainties of reconstructions in the south pacific for the times of anomalies 13 and 18 the best fit reconstructions and the uncertainty region for the anomaly 18 pole are in good agreement with previous work however the uncertainties in the anomaly 13 pole were substantially underestimated by previous investigators

archean block rotation in western karelia resolving dyke swarm patterns in metacraton karelia kola for a refined paleogeographic reconstruction of supercraton superia abstract rifting breakup and subsequent collision related to the ca 1 92 1 79 ga svecofennian orogeny fragmented and deformed the western margin of the archean karelia kola craton into four crustal blocks pudasjarvi iisalmi kuhmo and taivalkoski detailed quantification of svecofennian deformation is limited due to poorly exposed basement geology and an as yet incomplete dyke swarm record new u pb id tims geochronological results on baddeleyite and zircon are presented for three key mafic dykes from the pudasjarvi block namely the uolevinlehto myllykangas and sipojuntti dykes the age of the 325 trending uolevinlehto dyke is estimated at ca 2400 12 ma from discordant multigrain baddeleyite fractions showing it to be younger than ca 2450 ma dykes across karelia the 350 trending myllykangas dyke has a minimum age of 2135 2 3 6 3 7 ma based on chemically abraded zircon results from single baddeleyite grains provide a precise upper intercept age of 2128 9 1 2 ma for the 320 trending sipojuntti dyke our new u pb ages are integrated with those from the literature to define six major dyke swarms in the pudasjarvi block the nne trending ca 2 45 ga paajarvi nw trending ca 2 40 ga uolevinlehto nw trending ca 2 13 2 10 ga tohmajarvi wnw trending ca 2 07 ga palomaa nnw trending ca 1 98 ga paukkajanvaara and undated east west dykes trends of contemporaneous dyke swarms in the taivalkoski and kuhmo blocks however are systematically offset by 35 with subvertical dips offset dyke swarms record 35 clockwise vertical axis rotation of the pudasjarvi block relative to the interior of karelia consistent with dextral transpression during the svecofennian orogeny structural restoration of the pudasjarvi block improves the constraints on regional dyke swarm patterns and these are used to revise the position of the karelia kola craton within the context of the paleogeographic reconstruction of supercraton superia

oligocene and miocene global spatial trends of shallow marine carbonate architecture abstractthe present study provides the baseline status of the spatial distribution of carbonate platforms for the oligo miocene interval the resulting global trend quantitatively shows the decreas

sea level and vertical motion of continents from dynamic earth models since the late cretaceous dynamic earth models are used to better understand the impact of mantle dynamics on the vertical motion of continents and regional and global sea level change since the late cretaceous a hybrid approach combines inverse and forward models of mantle convection and accounts for the principal contributors to long term sea level change the evolving distribution of ocean floor age dynamic topography in oceanic and continental regions and the geoid we infer the relative importance of dynamic versus other factors of sea level change determine time dependent patterns of dynamic subsidence and uplift of continents and derive a sea level curve we find that both dynamic factors and the evolving distribution of sea floor age are important in controlling sea level we track the movement of continents over large scale dynamic topography by consistently mapping between mantle and plate frames of reference and we find that this movement results in dynamic subsidence and uplift of continents the amplitude of dynamic topography in continental regions is larger than global sea level in several regions and periods so that it has controlled regional sea level in north and south america and australia since the late cretaceous northern africa and arabia since the late eocene and southeast asia in the oligocene miocene eastern and southern africa have experienced dynamic uplift over the last 20 to 30 m y whereas siberia and australia have experienced cenozoic tilting the dominant factor controlling global sea level is a changing oceanic lithosphere production that has resulted in a large amplitude sea level fall since the late cretaceous with dynamic topography offsetting this fall