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Fred Davey

Bio: Fred Davey is an academic researcher from GNS Science. The author has contributed to research in topics: Crust & Plate tectonics. The author has an hindex of 32, co-authored 67 publications receiving 3188 citations. Previous affiliations of Fred Davey include Wellington Management Company & Pierre-and-Marie-Curie University.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a model of large-scale convection occurring throughout the TVZ is presented, in which the geothermal fields represent the upper portion of the rising, high-temperature, convective plumes.

403 citations

Journal ArticleDOI
18 Oct 2001-Nature
TL;DR: Sediment data from shallow marine cores in the western Ross Sea are presented that exhibit well dated cyclic variations, and which link the extent of the East Antarctic ice sheet directly to orbital cycles during the Oligocene/Miocene transition, suggesting that orbital influences at the frequencies of obliquity and eccentricity controlled the oscillations of the ice margin at that time.
Abstract: Between 34 and 15 million years (Myr) ago, when planetary temperatures were 3–4 °C warmer than at present and atmospheric CO2 concentrations were twice as high as today1, the Antarctic ice sheets may have been unstable2, 3, 4, 5, 6, 7. Oxygen isotope records from deep-sea sediment cores suggest that during this time fluctuations in global temperatures and high-latitude continental ice volumes were influenced by orbital cycles8, 9, 10. But it has hitherto not been possible to calibrate the inferred changes in ice volume with direct evidence for oscillations of the Antarctic ice sheets11. Here we present sediment data from shallow marine cores in the western Ross Sea that exhibit well dated cyclic variations, and which link the extent of the East Antarctic ice sheet directly to orbital cycles during the Oligocene/Miocene transition (24.1–23.7 Myr ago). Three rapidly deposited glacimarine sequences are constrained to a period of less than 450 kyr by our age model, suggesting that orbital influences at the frequencies of obliquity (40 kyr) and eccentricity (125 kyr) controlled the oscillations of the ice margin at that time. An erosional hiatus covering 250 kyr provides direct evidence for a major episode of global cooling and ice-sheet expansion about 23.7 Myr ago, which had previously been inferred from oxygen isotope data (Mi1 event5).

268 citations

Journal ArticleDOI
TL;DR: The Alpine Fault as discussed by the authors is the main active structure in the oblique continental collision zone of South Island, New Zealand and it is continuous at the surface for ∼800 km and accommodates ∼70% of current plate motion.

175 citations

Journal ArticleDOI
01 Aug 1986-Geology
TL;DR: The Hikurangi margin of eastern North Island, New Zealand, represents the feather edge of the Indian plate at its convergent boundary with the subducting Pacific plate, and a migrated seismic reflection profile across this margin clearly displays the structural evolution of an accretionary prism as discussed by the authors.
Abstract: The Hikurangi margin of eastern North Island, New Zealand, represents the feather edge of the Indian plate at its convergent boundary with the subducting Pacific plate. A migrated seismic reflection profile across this margin clearly displays the structural evolution of an accretionary prism. A 25-km-wide band of “protothrusts” is delineated between the toe of the slope and a converging seamount; this illustrates an early stage in the seaward propagation of a deformation front. Landward-tilted trench-slope basins are separated by ridges that have clearly defined thrusts, which appear to sole out at a decollement. The decollement continues at an angle of only 3° beneath the 150-km-wide margin to a depth of 14 km near the coast where it coincides with an onshore zone of high seismicity.

150 citations

Journal ArticleDOI
TL;DR: A compilation of marine geological and geophysical datasets suggests that Cook Strait developed when five sedimentary basins at a rapidly changing, obliquely convergent, plate boundary were moved into line and were linked by strong tidal scour in middle Pleistocene times.

131 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors present a digital model of the age, spreading rate, and asymmetry at each grid node by linear interpolation between adjacent seafloor isochrons in the direction of spreading.
Abstract: We present four companion digital models of the age, age uncertainty, spreading rates, and spreading asymmetries of the world's ocean basins as geographic and Mercator grids with 2 arc min resolution. The grids include data from all the major ocean basins as well as detailed reconstructions of back-arc basins. The age, spreading rate, and asymmetry at each grid node are determined by linear interpolation between adjacent seafloor isochrons in the direction of spreading. Ages for ocean floor between the oldest identified magnetic anomalies and continental crust are interpolated by geological estimates of the ages of passive continental margin segments. The age uncertainties for grid cells coinciding with marine magnetic anomaly identifications, observed or rotated to their conjugate ridge flanks, are based on the difference between gridded age and observed age. The uncertainties are also a function of the distance of a given grid cell to the nearest age observation and the proximity to fracture zones or other age discontinuities. Asymmetries in crustal accretion appear to be frequently related to asthenospheric flow from mantle plumes to spreading ridges, resulting in ridge jumps toward hot spots. We also use the new age grid to compute global residual basement depth grids from the difference between observed oceanic basement depth and predicted depth using three alternative age-depth relationships. The new set of grids helps to investigate prominent negative depth anomalies, which may be alternatively related to subducted slab material descending in the mantle or to asthenospheric flow. A combination of our digital grids and the associated relative and absolute plate motion model with seismic tomography and mantle convection model outputs represents a valuable set of tools to investigate geodynamic problems.

1,731 citations

Journal ArticleDOI
TL;DR: In this paper, a model-independent framework of genetic units and bounding surfaces for sequence stratigraphy has been proposed, based on the interplay of accommodation and sedimentation (i.e., forced regressive, lowstand and highstand normal regressive), which are bounded by sequence stratigraphic surfaces.

1,255 citations

Journal ArticleDOI
16 Jan 2003-Nature
TL;DR: In this simulation, declining Cenozoic CO2 first leads to the formation of small, highly dynamic ice caps on high Antarctic plateaux, and at a later time, a CO2 threshold is crossed, initiating ice-sheet height/mass-balance feedbacks that cause the ice caps to expand rapidly with large orbital variations, eventually coalescing into a continental-scale East Antarctic Ice Sheet.
Abstract: The sudden, widespread glaciation of Antarctica and the associated shift towards colder temperatures at the Eocene/Oligocene boundary (approximately 34 million years ago) (refs 1-4) is one of the most fundamental reorganizations of global climate known in the geologic record. The glaciation of Antarctica has hitherto been thought to result from the tectonic opening of Southern Ocean gateways, which enabled the formation of the Antarctic Circumpolar Current and the subsequent thermal isolation of the Antarctic continent. Here we simulate the glacial inception and early growth of the East Antarctic Ice Sheet using a general circulation model with coupled components for atmosphere, ocean, ice sheet and sediment, and which incorporates palaeogeography, greenhouse gas, changing orbital parameters, and varying ocean heat transport. In our model, declining Cenozoic CO2 first leads to the formation of small, highly dynamic ice caps on high Antarctic plateaux. At a later time, a CO2 threshold is crossed, initiating ice-sheet height/mass-balance feedbacks that cause the ice caps to expand rapidly with large orbital variations, eventually coalescing into a continental-scale East Antarctic Ice Sheet. According to our simulation the opening of Southern Ocean gateways plays a secondary role in this transition, relative to CO2 concentration.

1,029 citations

Journal ArticleDOI
TL;DR: In this article, a multivariate analysis is applied to this data set to isolate causal relationships among these parameters, which yields empirical quantitative relations that predict strain regime and strike-slip faulting in the overriding plate.
Abstract: Clues to the dynamics of the subduction process are found in the many measurable parameters of modern subduction zones. Based on a critical appraisal of the geophysical and geological literature, 26 parameters are estimated for each of 39 modern subduction zones. To isolate causal relationships among these parameters, multivariate analysis is applied to this data set. This analysis yields empirical quantitative relations that predict strain regime and strike-slip faulting in the overriding plate, maximum earthquake magnitude, Benioff zone length, slab dip, arc-trench gap, and maximum trench depth. Excellent correlation is found between length of the Benioff zone and the product of convergence rate and age of the downgoing slab. This relationship is consistent with the conductive heating model of Molnar et al. (1979), if the model is modified in one respect. The rate of heating of the slab is not constant; it is substantially slower during passage of the slab beneath the accretionary prism and overriding plate. The structural style in the overriding plate is determined by its stress state. Though the stress state of overriding plates cannot be quantified, one can classify each individual subduction zone into one of seven semiquantitative strain classes that form a continuum from strongly extensional (class 1, back-arc spreading) to strongly compressional (class 7, active folding and thrusting). This analysis indicates that strain class is probably determined by a linear combination of convergence rate, slab age, and shallow slab dip. Interplate coupling, controlled by convergence rate and slab age, is an important control on strain regime and the primary control on earthquake magnitude. Arc-parallel strike-slip faulting is a common feature of convergent margins, forming a forearc sliver between the strike-slip fault and trench. Optimum conditions for the development of forearc slivers are oblique convergence, a compressional environment, and a continental overriding plate. The primary factor controlling presence of strike-slip faulting is coupling; strongly oblique convergence is not required. The rate of strike-slip faulting is affected by both convergence obliquity and convergence rate. Maximum trench depth is a response to flexure of the underthrusting plate. The amount of flexural deflection at the trench depends on the vertical component of slab pull force, which is very sensitive to slab age and shallow slab dip. Shallow slab dip conforms to the cross-sectional shape of the overriding plate, which is controlled by width of the accretionary prism and duration of subduction. Deep slab dip is affected by the mantle trajectory established at shallow depth but may be modified by mantle flow. Much of the structural complexity of convergent margins is probably attributable to terrane juxtaposition associated with temporal changes in both forearc strike-slip faulting and strain regime. Empirical equations relating subduction parameters can provide both a focus for future theoretical studies and a conceptual and kinematic link between plate tectonics and the geology of subduction zones.

955 citations

Journal ArticleDOI
TL;DR: In this article, the relative velocities of 19 plates and continental blocks were derived from publicly available space geodetic (primarily GPS) data for the period 1993-2000, including an independent and rigorous estimate for GPS velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates.
Abstract: [1] We present a new global model for Recent plate velocities, REVEL, describing the relative velocities of 19 plates and continental blocks. The model is derived from publicly available space geodetic (primarily GPS) data for the period 1993–2000. We include an independent and rigorous estimate for GPS velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates. The velocity fields for North America, Eurasia, and Antarctica clearly show the effects of glacial isostatic adjustment, and Australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field. Two thirds of tested plate pairs agree with the NUVEL-1A geologic (3 Myr average) velocities within uncertainties. Three plate pairs (Caribbean–North America, Caribbean–South America, and North America–Pacific) exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in NUVEL-1A due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities. Most other differences probably reflect real velocity changes over the last few million years. Several plate pairs (Arabia–Eurasia, Arabia–Nubia, Eurasia–India) move more slowly than the 3 Myr NUVEL-1A average, perhaps reflecting long-term deceleration associated with continental collision. Several other plate pairs, including Nazca–Pacific, Nazca–South America and Nubia–South America, are experiencing slowing that began ∼25 Ma, the beginning of the current phase of Andean crustal shortening.

954 citations