Overriding-plate deformation during micro-continent accretion

2020 ◽  
Author(s):  
Zoltán Erdős ◽  
Ritske S. Huismans ◽  
Claudio Faccenna
Keyword(s):  
Plate Boundary ◽  
Slab Thickness ◽  
Plate Boundaries ◽  
Complex Structures ◽  
Model Experiments ◽  
Plate Deformation ◽  
Convergent Plate Boundaries ◽  
The Right ◽  
Back Arc ◽  
Subducting Slab

<p>Both divergent and convergent plate boundaries had been studied extensively throughout the last five decades. Among a host of other aspects came the realization, that given the right circumstances, a broad extensional basin can form behind a convergent plate boundary. The exact mechanisms triggering back-arc extension and why they are episodic, lasting only for tens of millions of years is still debated. The absolute and relative velocities of the plates, the age of the subducting oceanic plate and the inherited rheological properties of the back-arc lithosphere are all thought to be key players, shaping the dynamics of the fore-arc - back-arc systems.</p><p>Here we use 2D mantle scale plane-strain thermo-mechanical model experiments to investigate how the accretion of small continental crustal terrains onto the overriding plate affect the dynamics of the subducting slab and the deformation of the overriding plate.</p><p>Our results suggest that slab-retreat and back-arc extension can be achieved through the combination of slow convergence and micro-continent accretion. Back-arc extension during fast convergence is also possible through the subsequent accretion of more than one micro-continental terrain. Moreover, even the accretion of one such terrain can produce short (1-5 My) episodes of extension-contraction-quiescence in the overriding plate. These episodes are connected to slab break-off events, slab-interaction with upper mantle phase-change boundaries and variations in slab-pull due varying slab thickness.</p><p>Our model experiments also result in complex structures in the overriding plate where discrete outcrops from a single oceanic basin are preserved on the surface hundreds of kilometres apart. This indicates that in nature a simple accretion scenario could produce a surface geological record that is difficult to decipher. Our results compare favourably to observations from the Aegean back-arc basin.</p>

scholarly journals Beyond Plate Tectonics: Looking at Plate Deformation with Space Geodesy

1988 ◽  
Vol 129 ◽  
pp. 341-350
Author(s):  
Thomas H. Jordan ◽  
J. Bernard Minster
Keyword(s):  
Plate Tectonics ◽  
Plate Boundary ◽  
Point Of View ◽  
Space Geodesy ◽  
Plate Motion ◽  
Plate Boundaries ◽  
Measurement Systems ◽  
Motion Models ◽  
Plate Deformation ◽  
Continental Plate

We address the requirements that must be met by space-geodetic systems to place useful, new constraints on horizontal secular motions associated with the geological deformation of the earth's surface. Plate motions with characteristic speeds of about 50 mm/yr give rise to displacements that are easily observed by space geodesy. However, in order to improve the existing plate-motion models, the tangential components of relative velocities on interplate baselines must be resolved to an accuracy of < 3 mm/yr. Because motions considered small from a geodetic point of view have rather dramatic geological effects, especially when taken up as compression or extension of continental crust, detecting plate deformation by space-geodetic methods at a level that is geologically unresolvable places rather stringent requirements on the precision of the measurement systems: the tangential components on intraplate baselines must be observed with an accuracy of < 1 mm/yr. Among the measurements of horizontal secular motions that can be made by space geodesy, those pertaining to the rates within the broad zones of deformation characterizing the active continental plate boundaries are the most difficult to obtain by conventional ground-based geodetic and geological techniques. Measuring the velocities between crustal blocks to ± 5 mm/yr on 100-km to 1000-km length scales can yield geologically significant constraints on the integrated deformation rates across continental plate-boundary zones such as the western United States. However, baseline measurements in geologically complicated zones of deformation are useful only to the extent that the endpoints can be fixed in a local kinematical frame that includes major crustal blocks. For this purpose, the establishment of local geodetic networks around major VLBI and SLR sites in active areas should receive high priority.

Introduction

1981 ◽  
Vol 300 (1454) ◽  
pp. 219-222 ◽  
Keyword(s):  
National Committee ◽  
Plate Boundaries ◽  
Apparent Paradox ◽  
Suction Force ◽  
Arc Model ◽  
Geophysical Surveys ◽  
Convergent Plate Boundaries ◽  
The Many ◽  
Back Arc ◽  
The Western Pacific

The topic for this Discussion Meeting arose from the apparent paradox that extensional tectonics are commonly associated with ‘compressional’ plate boundaries. Elsasser (1970) first showed how extension could be associated with convergent plate boundaries, and subsequently (1971) he added a ‘suction force’ caused by the sinker effect of the cold subducting slab (see also Forsyth & Uyeda 1975). At about the same time, Karig (1970, 1971) suggested that several ‘marginal’ basins in the western Pacific had originated by back-arc spreading, an interpretation foreshadowed by Wegener (1924, p. 123). Karig (1972) also postulated that the isolated ridges within these back-arc basins were ‘remnant arcs’ inherited from earlier stages in their development. Subsequent drilling and detailed geophysical surveys have fully vindicated the back-arc spreading - remnant arc model. Despite these initial advances, the origin of extensional features associated with convergent plate boundaries is still poorly understood, and their distribution in space and time is not well known. This Discussion Meeting was therefore organized at the suggestion of one of us (A.G.S.) and under the auspices of the British National Committee for Geodynamics to air some of these problems. The objective was not to produce a global synthesis of all extensional features associated with convergent zones, but to review basic observations from areas that illustrate the many different facets of a phenomenon for which there is almost certainly no single explanation.

Geochemistry and timing of the marginal basin and arc magmatism in the Philippine Sea

1981 ◽  
Vol 300 (1454) ◽  
pp. 287-297 ◽  
Keyword(s):  
Complex Nature ◽  
Plate Boundaries ◽  
Island Arcs ◽  
Rock Composition ◽  
Philippine Sea ◽  
Mid Ocean Ridge ◽  
Convergent Plate Boundaries ◽  
Back Arc ◽  
Ocean Ridge ◽  
Drilling Project

Available data enable the recognition of three periods of back-arc crustal generation and three pulses of volcanic activity along the associated island arcs of the Philippine Sea. The geochemistry of the basalts from the back-arc basins of different ages indicates that in most cases they are identical to mid-ocean ridge basalts, and therefore should have similar sources and origins. In contrast, the island arc rock composition is variable in space and time, reflecting the different source and more complex nature of corresponding magmatism. Geomagnetic studies and recent Deep Sea Drilling Project results suggest an alternate sequence of back-arc and arc magmatic cycles. Both geochemical and geological observations provide important constraints on models of magmatism and extensions tectonics at convergent plate boundaries.

scholarly journals Regional Seismic Attribute Analysis and Tectono-Stratigraphy of Offshore South-Western Taranaki Basin, New Zealand

2021 ◽  
Author(s):  
◽  
Jan Robert Baur
Keyword(s):  
New Zealand ◽  
Deep Water ◽  
Middle Miocene ◽  
Plate Boundary ◽  
Water Area ◽  
Passive Margin ◽  
Extensional Faulting ◽  
Deep Water Area ◽  
Back Arc ◽  
Shelf Margin

<p>This study investigates the nature, origin, and distribution of Cretaceous to Recent sediment fill in the offshore Taranaki Basin, western New Zealand. Seismic attributes and horizon interpretations on 30,000 km of 2D seismic reflection profiles and three 3D seismic surveys (3,000 km²) are used to image depositional systems and reconstruct paleogeography in detail and regionally, across a total area of ~100,000 km² from the basin's present-day inner shelf to deep water. These data are used to infer the influence of crustal tectonics and mantle dynamics on the development of depocentres and depositional pathways. During the Cretaceous to Eocene period the basin evolved from two separate rifts into a single broad passive margin. Extensional faulting ceased before 85 Ma in the present-day deep-water area of the southern New Caledonia Trough, but stretching of the lithosphere was higher (β=1.5-2) than in the proximal basin (β<1.5), where faulting continued into the Paleocene (~60 Ma). The resulting differential thermal subsidence caused northward tilting of the basin and influenced the distribution of sedimentary facies in the proximal basin. Attribute maps delineate the distribution of the basin's main petroleum source and reservoir facies, from a ~20,000 km²-wide, Late Cretaceous coastal plain across the present-day deep-water area, to transgressive shoreline belts and coastal plains in the proximal basin. Rapid subsidence began in the Oligocene and the development of a foredeep wedge through flexural loading of the eastern boundary of Taranaki Basin is tracked through the Middle Miocene. Total shortening within the basin was minor (5-8%) and slip was mostly accommodated on the basin-bounding Taranaki Fault Zone, which detached the basin from much greater Miocene plate boundary deformation further east. The imaging of turbidite facies and channels associated with the rapidly outbuilding shelf margin wedge illustrates the development of large axial drainage systems that transported sediment over hundreds of kilometres from the shelf to the deep-water basin since the Middle Miocene. Since the latest Miocene, south-eastern Taranaki Basin evolved from a compressional foreland to an extensional (proto-back-arc) basin. This structural evolution is characterised by: 1) cessation of intra-basinal thrusting by 7-5 Ma, 2) up to 700 m of rapid (>1000 m/my) tectonic subsidence in 100-200 km-wide, sub-circular depocentres between 6-4 Ma (without significant upper-crustal faulting), and 3) extensional faulting since 3.5-3 Ma. The rapid subsidence in the east caused the drastic modification of shelf margin geometry and sediment dispersal directions. Time and space scales of this subsidence point to lithospheric or asthenospheric mantle modification, which may be a characteristic process during back-arc basin development. Unusual downward vertical crustal movements of >1 km, as inferred from seismic facies, paleobathymetry and tectonic subsidence analysis, have created the present-day Deepwater Taranaki Basin physiography, but are not adequately explained by simple rift models. It is proposed that the distal basin, and perhaps even the more proximal Taranaki Paleogene passive margin, were substantially modified by mantle processes related to the initiation of subduction on the fledgling Australia-Pacific plate boundary north of New Zealand in the Eocene.</p>

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