Tectonic and Geodynamic Evolution of the Northern Australian Margin and New Guinea (original) (raw)
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Dynamic subsidence of Eastern Australia during the Cretaceous
During the Early Cretaceous Australia's eastward passage over sinking subducted slabs induced widespread dynamic subsidence and formation of a large epeiric sea in the eastern interior. Despite evidence for convergence between Australia and the paleo-Pacific, the subduction zone location has been poorly constrained. Using coupled plate tectonic-mantle convection models, we test two end-member scenarios, one with subduction directly east of Australia's reconstructed continental margin, and a second with subduction translated~1000 km east, implying the existence of a back-arc basin. Our models incorporate a rheological model for the mantle and lithosphere, plate motions since 140 Ma and evolving plate boundaries. While mantle rheology affects the magnitude of surface vertical motions, timing of uplift and subsidence depends on plate boundary geometries and kinematics. Computations with a proximal subduction zone result in accelerated basin subsidence occurring 20 Myr too early compared with tectonic subsidence calculated from well data. This timing offset is reconciled when subduction is shifted eastward. Comparisons between seismic tomography and model temperature cross-sections, and an absence of subduction zone volcanism in eastern Australia in the Early Cretaceous provide support for the back-arc basin scenario.
Australia's northwestern passive margin intersects the eastern termination of the Java trench segment of the Sunda arc subduction zone and the western termination of Timor trough along the Banda arc tectonic collision zone. Differential relative motion between the Sunda arc subduction zone and the Banda arc collision zone has reactivated the former rifted margin of northwestern Australia evidenced by Pliocene to Quaternary age deformation along a 1400 km long offshore fault system. The fault system has higher rates of seismicity than the adjacent nonextended crustal terranes, has produced the largest historical earthquake in Australia (1941 M L 7.3 Meeberrie event), and is dominated by focal mechanism solutions consistent with dextral motion along northeast trending fault planes. The faults crosscut late Miocene unconformities that are eroded across middle Miocene inversion structures suggesting multiple phases of Neogene and younger fault reactivation. Onset of deformation is consistent with the timing of the collision of the Scott Plateau part of the passive continental margin with the former Banda trench between 3.0 Ma and present. The range of estimated maximum horizontal slip rates across the zone is ~1.4 to 2.6 mm yr À1 , at the threshold of geodetically detectable motion, yet significant with respect to an intraplate tectonic setting. The folding and faulting along this part of the continental margin provides an example of intraplate deformation resulting from kinematic transitions along a distant plate boundary and demonstrates the presence of a youthful evolving intraplate fault system within the Indo-Australian plate.
Numerous extensional faults offset the passive margin strata of the northern Bonaparte Basin. This extensional deformation has been attributed to lithospheric flexure of the descending Australian Plate, in an overall convergence setting. Here we use an extensive 2D and 3D seismic dataset calibrated with well biostratigraphy and strontium (Sr) isotope age data to constrain the timing of deformation along the northern Australian margin during the Neogene. Analysis of fault throw and differential thickness variations give new insights on the propagation and slip history of the faults. Along-dip throw profiles exhibit 'D' shape distributions, skewed towards the top. Positive throw gradients above the throw maxima, coinciding with intervals of growth strata, indicate multiphase fault activity. Results indicate that post-rift extensional deformation initiated during the latest Miocene (ca. 6 Ma). The development of the modern Timor Trough (as a foreland basin) and Cartier Trough also commenced during this period. A second episode of increased tectonic activity occurred around the Pliocene–Quaternary boundary (ca. 3 Ma), and the deformation continued intermittently to the present-day. These new results are in agreement with the timing of initiation of collision between the Australian Plate and the Banda Arc and uplift of the Timor Island, recently derived from stratigraphic analysis in Timor. These regional tectonic events have profoundly affected the paleogeography of the Timor Sea and may explain major changes in oceanic circulation and climate during the Neogene.
Subduction history in the Melanesian Borderlands region, SW Pacific
2012
The easternmost Coral Sea region is an underexplored area at the northeasternmost corner of the Australian plate. Situated between the Mellish Rise, southern Solomon Islands, northern Vanuatu and New Caledonia, it represents one of the most dynamic and tectonically complex submarine regions of the world. Interactions between the Pacific and Australian plate boundaries have resulted in an intricate assemblage of deep oceanic basins and ridges, continental fragments and volcanic products; yet there is currently no clear conceptual framework to describe their formation. Due to the paucity of geological and geophysical data from the area to constrain plate tectonic models, a novel approach has been developed whereby the history of subduction based on a plate kinematic model is mapped to present-day seismic tomography models. A plate kinematic model, which includes a self-consistent mosaic of evolving plate boundaries through time is used to compute plate velocity fields and palaeooceanic age grids for each plate in 1 million year intervals. Forward geodynamic models, with imposed surface plate velocity constraints are computed using the 3D spherical finite element convection code CitcomS. A comparison between the present-day mantle temperature field predicted by these geodynamic models with seismic tomography suggests that the kinematic model for the subduction history in the eastern Coral Sea works well for the latest Cenozoic but fails to predict seismically fast material in the lower mantle (indicative of cold, subducted material) imaged in seismic tomography models. This implies that the location and nature of the plate boundaries in the eastern Coral Sea used in these models requires further refinement. A quantified tectonic framework and subduction history of the region will assist in assessing hydrocarbon and mineral resource potential of northeastern Australia and Australia’s Pacific island neighbours, the eastward extent of Australian continental lithosphere and will help place further constrains on the subsidence and uplift history of Australia’s eastern sedimentary basins and carbonate-capped plateaus.
Plate tectonics and sedimentary basins – University of Sydney and the Basin Genesis Hub
ASEG Preview, 2018
The ARC Basin GENESIS Hub (BGH) is a 5-year Industry Transformation Research Hub supported by the Australian Research Council (ARC) and 5 industry partners, aimed at developing and applying next generation computer models to fine-tune our understanding of the structure and evolution of sedimentary basins. The Hub is based at the University of Sydney’s EarthByte research group (www.earthbyte.org), led by Dietmar Müller and Patrice Rey, with additional nodes at the University of Melbourne (led by Louis Moresi), Curtin University (led by Chris Elders), the California Institute of Technology (led by Michael Gurnis) and Geoscience Australia (led by Karol Czarnota). The Hub’s unique strength is in connecting global plate tectonic and geodynamic models to models of the evolution of individual basins and their hinterlands. This requires linking disparate geological and geophysical data sets with several simulations and modelling codes and their outputs. A central theme in the Hub is understanding the origin, and destruction, of topography. Surface topography represents the source of sediments that ultimately end up in sedimentary basins. Therefore, we are trying to understand how surface topography or accommodation space is created or destroyed via combinations of lithospheric deformation, mantle convection, erosion and sedimentation, constrained by a range of observations. This article portrays the software and new basin modelling workflows being developed in this research centre, with particular emphasis on the Hub’s early career researchers.
Tectonophysics, 1994
The Adelaide, Lachlan and New England fold belts of eastern Australia record the continental growth of eastern Gondwanaland during the Palaeozoic. The New England Fold Belt (NEFB) represents a tectonic collage formed by subduction/accretion during the Late Paleozoic, but contains remnants of subduction-related rocks that date from the Cambrian. The Lachlan Fold Belt (LFB) developed inboard from the NEFB, initially as an amalgam of Proterozoic continental and Cambrian oceanic fragments that formed by rift and drift at the leading edge of eastern Gondwanaland. Convergent tectonism at N 500 Ma welded the fragments to the craton and formed the Adelaide fold belt. Oceanward dispersal of detritus across the LFB produced an overlap assemblage of quartzose Ordovician turbidites, and a new subduction zone developed at the eastern margin. The tectonic setting was similar to the modern Philippines plate of the western Pacific. Behind-the-arc, Silurian-Devonian convergent tectonics converted the 1700-2000~km-wide continental margin of the Proto-LFB into a-750~km-wide, thinskinned , fold-magmatic belt within 60 Ma. The driving force was delamination, which produced a ubiquitous basaltic underplate that generated: (1) regional low-P metamorphism; (2) local anticlockwise P-T-t paths and crustal-scale isobaric cooling; (3) voluminous syn-to late-tectonic granitoids, emplaced at rates approximately twice that of modern arcs; and (4) normal thickness crust, despite an average of N 60% shortening. Delamination occurred in two separate areas originally-1000 km apart, first in the eastern, then in the western part of the LFB. The LFB and its northern counterpart, the Thomson fold belt, represent approximately one-fifth of the Australian continent, and evolved from dispersed fragments into stable continental crust in N 300 Ma. Such rapid growth rates are typical of the 2.7-2.5 Ga and 1.9-1.7 Ga periods, when voluminous, widespread granitoids and large turbidite-dominated, low-P metamorphic belts were produced in settings that are not obviously subduction-related. Therefore, a similar process of rift-drift-delamination (RIDDEL tectonics) may have periodically operated throughout Earth history.
Proceedings of the Ocean Drilling Program, 135 Scientific Results, 1994
Sedimentary sections recovered from the Tonga platform and forearc during Ocean Drilling Program Leg 135 provide a record of the sedimentary evolution of the active margin of the Indo-Australian Plate from late Eocene time to the Present. Facies analyses of the sediments, coupled with interpretations of downhole Formation MicroScanner logs, allow the complete sedimentary and subsidence history of each site to be reconstructed. After taking into account the water depths in which the sediments were deposited and their subsequent compaction, the forearc region of the Tofua Arc (Site 841) can be seen to have experienced an initial period of tectonic subsidence dating from 35.5 Ma. Subsidence has probably been gradual since that time, with possible phases of accelerated subsidence, starting at 16.2 and 10.0 Ma. The Tonga Platform (Site 840) records only the last 7.0 Ma of arc evolution. However, the increased accuracy of paleowater depth determinations possible with shallow-water platform sediments allows the resolution of a distinct increase in subsidence rates at 5.30 Ma. Thus, sedimentology and subsidence analyses show the existence of at least two, and possibly four, separate subsidence events in the forearc region. Subsidence dating from 35.5 Ma is linked to rifting of the South Fiji Basin. Any subsidence dating from 16.2 Ma at Site 841 does not correlate with another known tectonic event and is perhaps linked to localized extensional faulting related to slab roll back during steady-state subduction. Subsidence from 10.0 Ma coincides with the breakup of the early Tertiary Vitiaz Arc because of the subduction polarity reversal in the New Hebrides and the subsequent readjustment of the plate boundary geometry. More recently, rapid subsidence and deposition of a upward-fining cycle from 5.30 Ma to the Present at Site 840 is thought to relate to rifting of the Lau Basin. Sedimentation is principally controlled by tectonic activity, with variations in eustatic sea level playing a significant, but subordinate role. Subduction of the Louisville Seamount Chain seems to have disrupted the forearc region locally, although it had only a modest effect on the subsidence history and sedimentation of the Tonga Platform as a whole.
Marine Geology, 1977
A comprehensive study of the last 75 m.y. of plate tectonics history has been undertaken for the region south of 30 ° S in the South Pacific, Southeast Indian Ocean and the Tasman Sea. Some aspects of plate boundary evolution have been clarified by our compilation and examination of available marine geophysical data. Reidentification of magnetic lineations in the southern Tasman basin shows that the controversial interval of subduction of Tasman basin crust along the east Australian margin that was previously proposed is no longer necessary. A comparison of Cenozoic magnetic lineations from both sides of the easternmost spreading segment of southeast Indian ridge indicates that a portion of the Indian plate younger than anomaly 10 (32 m.y.B.P.) is missing. We suggest that the missing crust was either subducted beneath or captured by the Pacific plate. Older lineations on the Indian plate out to about anomaly 21 have greater alongstrike lengths than their counterparts on the Antarctic plate. The difference is due to an interval of crustal accretion at the Indian-Pacific plate boundary in the Early to Middle Tertiary. In the South Pacific, the Antarctic plate may not have extended northeast of the Eltanin fracture zone system prior to anomaly 29 (69 m.y.B.P.). Subduction of oceanic lithosphere was probably occurring beneath the Antarctic peninsula and eastern Ellsworth Land parts of the Antarctic plate at that time. Between anomaly-29 time and a major reorganization of plate boundaries in the Late Oligocene, plate interactions occurred in the central South Pacific between the Pacific, Farallon, Antarctic, Aluk and possibly a fifth plate. Spreading rate calculations for the Early Oligocene indicate that a simple three-plate system involving the Pacific, Farallon and Antarctic plates is difficult to maintain unless highly asymmetric spreading occurred at the Farallon-Antarctic boundary in the Early Oligocene. Further to the southeast in the Bellingshausen basin, spreading occurred along segments of the Antarctic-Aluk plate boundary beginning at about anomaly-29 time. Collisions of segments of this boundary with the trench along the Antarctic peninsula occurred in the Early and Middle Tertiary and resulted in the total disappearance of portions of Aluk plate. The collisions brought Antarctic-Aluk ridge segments into contact with Antarctic-Aluk trench segments with resulting stabilization of the Antarctic continental margin.
WABS, 2019
The post-Lower Permian succession of the Perth Basin and Westralian Superbasin can be directly related to the plate tectonic evolution of the Gondwanan Super-continent. In the Late Permian to Albian the northern edge of Gondwana continued to break into microplates that migrated to the north and were accreted into what is today the southeastern Asia (Burma–China) region. These separation events are recorded as a series of stratigraphically distinct transgressions (corresponding to the initial stretching of the asthenosphere and acceleration of subsidence rates) followed by rapid regressions (when new oceanic crust was emplaced in thinned continental crust causing uplifts of large continental masses). Because the events are synchronous across large regions, and may be identified from specific log and seismic signatures, the intensity of stratigraphically related transgressive/regressive cycles varies, depending on the distance from the break-up centres and these cycles allow the ident...