NNR‐MORVEL56, which is a set of angular velocities of 56 plates relative to the unique reference frame in which there is no net rotation of the lithosphere, is determined. The relative angular ...velocities of 25 plates constitute the MORVEL set of geologically current relative plate angular velocities; the relative angular velocities of the other 31 plates are adapted from Bird (2003). NNR‐MORVEL, a set of angular velocities of the 25 MORVEL plates relative to the no‐net rotation reference frame, is also determined. Incorporating the 31 plates from Bird (2003), which constitute 2.8% of Earth's surface, changes the angular velocities of the MORVEL plates in the no‐net‐rotation frame only insignificantly, but provides a more complete description of globally distributed deformation and strain rate. NNR‐MORVEL56 differs significantly from, and improves upon, NNR‐NUVEL1A, our prior set of angular velocities of the plates relative to the no‐net‐rotation reference frame, partly due to differences in angular velocity at two essential links of the MORVEL plate circuit, Antarctica‐Pacific and Nubia‐Antarctica, and partly due to differences in the angular velocities of the Philippine Sea, Nazca, and Cocos plates relative to the Pacific plate. For example, the NNR‐MORVEL56 Pacific angular velocity differs from the NNR‐NUVEL1A angular velocity by a vector of length 0.039 ± 0.011° a−1 (95% confidence limits), resulting in a root‐mean‐square difference in velocity of 2.8 mm a−1. All 56 plates in NNR‐MORVEL56 move significantly relative to the no‐net‐rotation reference frame with rotation rates ranging from 0.107° a−1 to 51.569° a−1.
Key Points
31 plates are added to MORVEL to describe geologically current plate motion
The no‐net‐rotation frame for these plates, NNR‐MORVEL56, is determined
NNR‐MORVEL56 differs significantly from NNR‐NUVEL1A and other realizations
A vast ocean basin has spanned the region between the Americas, Asia and Australasia for well over 100Myr, represented today by the Pacific Ocean. Its evolution includes a number of plate ...fragmentation and plate capture events, such as the formation of the Vancouver, Nazca, and Cocos plates from the break-up of the Farallon plate, and the incorporation of the Bellingshausen, Kula, and Aluk (Phoenix) plates, which have been studied individually, but never been synthesised into one coherent model of ocean basin evolution. Previous regional tectonic models of the Pacific typically restrict their scope to either the North or South Pacific, and global kinematic models fail to incorporate some of the complexities in the Pacific plate evolution (e.g. the independent motion of the Bellingshausen and Aluk plates), thereby limiting their usefulness for understanding tectonic events and processes occurring in the Pacific Ocean perimeter. We derive relative plate motions (with 95% uncertainties) for the Pacific–Farallon/Vancouver, Kula–Pacific, Bellingshausen–Pacific, and early Pacific–West Antarctic spreading systems, based on recent data including marine gravity anomalies, well-constrained fracture zone traces and a large compilation of magnetic anomaly identifications. We find our well-constrained relative plate motions result in a good match to the fracture zone traces and magnetic anomaly identifications in both the North and South Pacific. In conjunction with recently published and well-constrained relative plate motions for other Pacific spreading systems (e.g. Aluk–West Antarctic, Pacific-Cocos, recent Pacific–West Antarctic spreading), we explore variations in the age of the oceanic crust, seafloor spreading rates and crustal accretion and find considerable refinements have been made in the central and southern Pacific. Asymmetries in crustal accretion within the overall Pacific basin (where both flanks of the spreading system are preserved) have typically deviated less than 5% from symmetry, and large variations in crustal accretion along the southern East Pacific Rise (i.e. Pacific–Nazca/Farallon spreading) appear to be unique to this spreading corridor. Through a relative plate motion circuit, we explore the implied convergence history along the North and South Americas, where we find that the inclusion of small tectonic plate fragments such as the Aluk plate are critical for reconciling the history of convergence with onshore geological evidence.
In this paper we present a global model (GSRM-1) of both horizontal velocities on the Earth's surface and horizontal strain rates for almost all deforming plate boundary zones. A model strain rate ...field is obtained jointly with a global velocity field in the process of solving for a global velocity gradient tensor field. In our model we perform a least-squares fit between model velocities and observed geodetic velocities, as well as between model strain rates and observed geological strain rates. Model velocities and strain rates are interpolated over a spherical Earth using bi-cubic Bessel splines. We include 3000 geodetic velocities from 50 different, mostly published, studies. Geological strain rates are obtained for central Asia only and they are inferred from Quaternary fault slip rates. For all areas where no geological information is included a priori constraints are placed on the style and direction (but not magnitude) of the model strain rate field. These constraints are taken from a seismic strain rate field inferred from (normalized) focal mechanisms of shallow earthquakes. We present a global solution of the second invariant of the model strain rate field as well as strain rate solutions for a few selected plate boundary zones. Generally, the strain rate tensor field is consistent with geological and seismological data. With the assumption of plate rigidity for all areas other than the plate boundary zones we also present relative angular velocities for most plate pairs. We find that in general there is a good agreement between the present-day plate motions we obtain and long-term plate motions, but a few significant differences exist. The rotation rates for the Indian, Arabian and Nubian plates relative to Eurasia are 30, 13 and 50 per cent slower than the NUVEL-1A estimate, respectively, and the rotation rate for the Nazca Plate relative to South America is 17 per cent slower. On the other hand, Caribbean–North America motion is 76 per cent faster than the NUVEL-1A estimate. While crustal blocks in the India–Eurasia collision zone move significantly and self-consistently with respect to bounding plates, only a very small motion is predicted between the Nubian and Somalian plates. By integrating plate boundary zone deformation with the traditional modelling of angular velocities of rigid plates we have obtained a model that has already been proven valuable in, for instance, redefining a no-net-rotation model of surface motions and by confirming a global correlation between seismicity rates and tectonic moment rates along subduction zones and within zones of continental deformation.
The heterogeneous Sundaland region was assembled by closure of Tethyan oceans and addition of continental fragments. Its Mesozoic and Cenozoic history is illustrated by a new plate tectonic ...reconstruction. A continental block (Luconia–Dangerous Grounds) rifted from east Asia was added to eastern Sundaland north of Borneo in the Cretaceous. Continental blocks that originated in western Australia from the Late Jurassic are now in Borneo, Java and Sulawesi. West Burma was not rifted from western Australia in the Jurassic. The Banda (SW Borneo) and Argo (East Java–West Sulawesi) blocks separated from western Australia and collided with the SE Asian margin between 110 and 90Ma, and at 90Ma the Woyla intra-oceanic arc collided with the Sumatra margin. Subduction beneath Sundaland terminated at this time. A marked change in deep mantle structure at about 110°E reflects different subduction histories north of India and Australia since 90Ma. India and Australia were separated by a transform boundary that was leaky from 90 to 75Ma and slightly convergent from 75 to 55Ma. From 80Ma, India moved rapidly north with north-directed subduction within Tethys and at the Asian margin. It collided with an intra-oceanic arc at about 55Ma, west of Sumatra, and continued north to collide with Asia in the Eocene. Between 90 and 45Ma Australia remained close to Antarctica and there was no significant subduction beneath Sumatra and Java. During this interval Sundaland was largely surrounded by inactive margins with some strike-slip deformation and extension, except for subduction beneath Sumba–West Sulawesi between 63 and 50Ma. At 45Ma Australia began to move north; subduction resumed beneath Indonesia and has continued to the present. There was never an active or recently active ridge subducted in the Late Cretaceous or Cenozoic beneath Sumatra and Java. The slab subducted between Sumatra and east Indonesia in the Cenozoic was Cretaceous or older, except at the very western end of the Sunda Arc where Cenozoic lithosphere has been subducted in the last 20million years. Cenozoic deformation of the region was influenced by the deep structure of Australian fragments added to the Sundaland core, the shape of the Australian margin formed during Jurassic rifting, and the age of now-subducted ocean lithosphere within the Australian margin.
The Jiamusi and Songnen blocks converged in the easternmost segment of the Central Asian Orogenic Belt as a result of the subduction and subsequent closure of the Mudanjiang oceanic plate during the ...Permian–Jurassic. The Mudanjiang suture zone was later directly affected by subductions of the Paleo-Pacific plate and Pacific plate and is therefore an ideal place to study the subduction polarity and later transformation of a paleo-suture zone. Using three-dimensional inversion of magnetotelluric data collected along a 160-km-long profile across the Mudanjiang suture zone, we established a resistivity model of the suture zone and adjacent area. Our results reveal the subduction polarity and subduction trace of the Mudanjiang oceanic plate and provide geoelectrical evidence for reactivation of the Mudanjiang suture zone induced by the (Paleo-)Pacific plate subduction. The suture zone shows a complex conductive structure. The west-dipping crustal-scale conductor beneath the Songnen-Jiamusi collision zone represents the fossil subduction zone and indicates the westward subduction polarity of the Mudanjiang oceanic plate. Furthermore, the Mudanjiang fault identified by surface geology does not fully represent the deep structure of the Mudanjiang suture zone. The definition of the suture zone should be extended to the whole conductive region with a lateral extent of ∼70 km. Solid conductive minerals beneath the arc in front of the subduction zone were exhumated up from deep to the upper crust. The “chimney”-shaped conductor connected with the mantle represents the intrusive pathways of mantle-derived materials, suggesting that the Mudanjiang suture zone was reactivated by subductions of the Paleo-Pacific plate and Pacific plate, leading to remelting of the cooled and crystallized materials in the pathways. Therefore, subduction of the (Paleo-)Pacific plate destroyed the lithospheric structure of the paleo collision zone in the eastern segment of the Central Asian orogenic belt, and the large-scale crustal conductor beneath the suture zone reflects reactivation of the paleo-suture zone.
Oceanic plates are growing through narrow boundaries, such as mid-ocean ridges and transform faults. However, the discovery of diffuse plate boundary suggests another type of plate boundary that ...accommodates difference in plate motion via internal deformation. Along the Central and Southeast Indian ridges, for example, the Capricorn and Macquarie microplates exhibit widespread diffuse boundaries and hence divide the Indo-Australian Plate further into the Indian, Australian, Capricorn, and Macquarie plates. As for microplates distributed along the East Pacific Rise and Pacific-Antarctic Ridge in the Pacific Ocean, however, the typical plate boundaries surrounding the given microplate are distinctly established. Global plate reorganization involving the changes in plate motion or in spreading direction can be accommodated by forming a microplate through ridge extinction, ridge propagation, and pseudofault formation. However, relations between these tectonic processes have not been quantitatively assessed. In particular, we aim to examine tectonic constrains on the formation processes of microplates with diffuse plate boundary. In this study, we compare plate size, plate age, full-spreading rates, thermal structures, total rotation, and rotation rate for the 9 microplates including extinct plates (i.e., Capricorn, Macquarie, and Mammerickx* microplates in the Indian and Southern Oceans; Galapagos, Easter, Juan Fernandez, Bauer*, Friday*, and Selkirk* microplates in the Pacific Ocean; extinct plates are denoted with asterisks). From this comparison, we find that the microplate formation would require certain tectonic conditions (e.g., full-spreading rates faster than 70–80 mm/yr and rotation rates faster than 5–6°/m.y.) to evolve into an independent and rigid plate with respect to the neighboring plates. If the conditions are not met, the same tectonic reorganization would result in a microplate with diffuse plate boundaries.
A reorganization centered on the Pacific plate occurred ~53–47 million years ago. A “top‐down” plate tectonic mechanism, complete subduction of the Izanagi plate, as opposed to a “bottom‐up” mantle ...flow mechanism, has been proposed as the main driver. Verification based on marine geophysical observations is impossible as most ocean crust recording this event has been subducted. Using a forward modeling approach, which assimilates surface plate velocities and shallow thermal structure of slabs into mantle flow models, we show that complete Izanagi plate subduction and margin‐wide slab detachment induced a major change in sub‐Pacific mantle flow, from dominantly southward before 60 Ma to north‐northeastward after 50 Ma. Our results agree with onshore geology, mantle tomography, and the inferred motion of the Hawaiian hot spot and are consistent with a plate tectonic process driving the rapid plate‐mantle reorganization in the Pacific hemisphere between 60 and 50 Ma. This reorganization is reflected in tectonic changes in the Pacific and surrounding ocean basins.
Key Points
Pacific Eocene reorganization was triggered by a ridge subduction event
Izanagi plate subduction and slab detachment altered Pacific mantle flow
Our geodynamic models agree with seismic tomography and onshore geology
Reconstructions of motions of the Nazca, South American, and Indian plates record short‐duration (≲10 Myr) variations in angular velocity, which enable a vector‐based test of the hypothesis that ...mountain uplift can cause changes in plate motion. Reductions in velocity of Nazca and South America between ∼12 and 6 Ma coincide with a phase of rapid surface uplift in the Central Andes. Decrease in the rate of India's convergence with Eurasia between ∼20 and 10 Ma corresponds to an increase in gravitational potential energy per unit area (GPE) within Tibet, marked by a transition from crustal thickening to thinning. The vectorial test shows that, in each case, the only change in driving force capable of balancing the change in basal drag is an increased resistance along the convergent boundary to the plate. Changes in GPE associated with mountain uplift provide a calibration for basal drags on plates. Basal tractions of ∼0.1–1 MPa provide resisting forces comparable in magnitude to driving forces from GPE variation in ocean lithosphere. The rapid change in motion of the Indian plate between about 48 and 41 Ma is explained by the juxtaposition of the Indian continent against the Andean‐type margin of the Transhimalaya and reduction in driving force due to loss of the slab. The net slab driving force lost was ∼2–4 TN m−1, in agreement with previous studies suggesting that forces resisting slabs' penetration into the mantle largely offset their negative buoyancy.
Key Points
Calculation of forces required to cause rapid changes in plate motion test the hypothesis that some stem from increase in gravitational potential energy (GPE) of mountains
Rapid decreases in velocity of Nazca, South American, and Indian plates require increases in resistance at their convergent boundaries
Geological evidence shows that the Miocene decreases in velocity were contemporaneous with increases in GPE of the Andes and Tibet
Mantle dynamics in the Mediterranean Faccenna, Claudio; Becker, Thorsten W.; Auer, Ludwig ...
Reviews of geophysics (1985),
September 2014, Volume:
52, Issue:
3
Journal Article
Peer reviewed
Open access
The Mediterranean offers a unique opportunity to study the driving forces of tectonic deformation within a complex mobile belt. Lithospheric dynamics are affected by slab rollback and collision of ...two large, slowly moving plates, forcing fragments of continental and oceanic lithosphere to interact. This paper reviews the rich and growing set of constraints from geological reconstructions, geodetic data, and crustal and upper mantle heterogeneity imaged by structural seismology. We proceed to discuss a conceptual and quantitative framework for the causes of surface deformation. Exploring existing and newly developed tectonic and numerical geodynamic models, we illustrate the role of mantle convection on surface geology. A coherent picture emerges which can be outlined by two, almost symmetric, upper mantle convection cells. The downwellings are found in the center of the Mediterranean and are associated with the descent of the Tyrrhenian and the Hellenic slabs. During plate convergence, these slabs migrated backward with respect to the Eurasian upper plate, inducing a return flow of the asthenosphere from the back‐arc regions toward the subduction zones. This flow can be found at large distance from the subduction zones and is at present expressed in two upwellings beneath Anatolia and eastern Iberia. This convection system provides an explanation for the general pattern of seismic anisotropy in the Mediterranean, first‐order Anatolia, and Adria microplate kinematics and may contribute to the high elevation of scarcely deformed areas such as Anatolia and eastern Iberia. More generally, the Mediterranean is an illustration of how upper mantle, small‐scale convection leads to intraplate deformation and complex plate boundary reconfiguration at the westernmost terminus of the Tethyan collision.
Key Points
Subduction drives the evolution of the MediterraneanTyrrhenian and Hellenic subduction zones induce a large‐scale return flowSurface deformation is coupled to and drived by upper mantle return flow
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