Geo★ Down Under

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Geo★ Down Under is an open and self-organising community loosely coordinated by Louis Moresi of the ANU. We welcome new writers, editors and supporters. If you are interested, drop us a line: editors_gdu@agora.geo-down-under.geoscience.education We receive support from AuScope to power the engines behind the website and the community forum and mailing lists. AuScope also provides us with writing support … Read more…

Linking rift propagation barriers to excess magmatism at volcanic rifted margins

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Koopmann etal 2014 Model EvolutionCitation
Koopman, H., Brune, S., Franke, D. and Breuer. 2014. Linking rift propagation barriers to excess magmatism at volcanic rifted margins. Geology (Pre-Issue Publication 15. Oct), doi: 10.1130/G36085.

Summary
Break-up–related extrusive magmatism, imaged in reflection seismic data as seaward-dipping reflectors (SDRs), extends sym- metrically along the volcanic margins of the Atlantic Ocean. Recent research found distinct along-margin variations in the distribution of SDRs, and abundance of volcanic material was found to be spatially linked to transfer fault systems. These segmented the propagating rift that later developed into the ocean, and are interpreted as rift propa- gation barriers. Based on these observations, we develop a numeri- cal model, which shows that rift-parallel mantle flow and locally enhanced rates of volcanism are the result of delays in rift propaga- tion and segmented opening. … Read more…

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Science – New global marine gravity model from Cryo-Sat-2 and Jason-1 reveals buried tectonic structure

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Sandwell, D. T., Müller, R. D., Smith, W. H., Garcia, E., & Francis, R. (2014). New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure. science, 346(6205), 65-67. doi: 10.1126/science.1258213.

New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure

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New GPlates Portal available

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GPlates Portal Figure

EarthByte have launched a new cloud-based GPlates Web Portal that was used by almost 40 000 users over the last long-weekend! It took GPlates software over ten years to get that many users, so this is a huge achievement and also makes GPlates accessible to a broader audience! The GPlates portal can be used to … Read more…

New global marine gravity model, Sandwell et al. (2014)

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Indian Ocean View Westward from AustraliaCitation
Sandwell, D. T., Müller, R. D., Smith, W. H. F., Garcia, E. and Francis, R. 2014. New global marine gravity model from Cryo-Sat-2 and jason-1 reveals buried tectonic structure. Science, Vol. 346, 6205, pp. 65-67, doi: 10.1126/science.1258213.

Summary
New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure.

View the new gravity map in an online 3D portal!

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 … Read more…

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Post-Jurassic tectonic evolution of southeast Asia from Zahirovic et al. (2014)

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Asia Zahirovic 20maCitation
Zahirovic, S., Seton, M., and Müller, R. D., (2014). The Cretaceous and Cenozoic tectonic evolution of Southeast Asia: Solid Earth (EGU).

Summary
Tectonic reconstructions of Southeast Asia have given rise to numerous controversies that include the accretionary history of Sundaland and the enigmatic tectonic origin of the Proto South China Sea. We assimilate a diversity of geological and geophysical observations into a new regional plate model, coupled to a global model, to address these debates.

Our approach takes into account terrane suturing and accretion histories, the location of subducted slabs imaged in mantle tomography in order to constrain the evolution of regional subduction zones, as well as plausible absolute and relative plate velocities and tectonic driving mechanisms. … Read more…

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The tectonic stress field evolution of India since the Oligocene

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Muller etal India Paleostress Graphical AbstractCitation
Müller, R. D., Yatheesh, V., & Shuhail, M. (2014). The tectonic stress field evolution of India since the Oligocene. Gondwana Research.

Summary
We use a 2 dimensional finite element model with heterogeneous elastic strengths in continental areas to model the regional stress field orientation and relative magnitudes in and around India for 33 Ma, 20 Ma and the present day. The large-scale geological structure of India is embedded in our model by using published outlines of cratons, fold belts and basins, associated with estimates of their relative strengths, enabling the modelling of stress field deflections along interfaces between relatively strong and weak tectonic elements through time. … Read more…

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Gabriella McDonald receives travel grant to visit Canada

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Honours student Gabby McDonald was one of 16 students world-wide to be awarded a Student Field Trip Travel Grant from the Society of Economic Geologists to participate in “Archean Base and Precious Metal Deposits, Southern Abitibi Greenstone Belt, Canada”. The field trip was lead by a team of Canadian experts and travelled from Timmins to … Read more…

Evolution of stress and fault patterns in oblique rift systems: 3D numerical lithospheric-scale experiments from rift to breakup

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Rifting involves complex normal fault systems that are controlled by extension direction, reactivation of pre-rift structures, sedimentation, and dyke dynamics. The relative impact of these factors on the observed fault pattern, however, is difficult to deduce from field-based studies alone.

This study provides insight in crustal stress patterns and fault orientations by employing a laterally homogeneous, 3D rift setup with constant extension velocity. The presented numerical forward experiments cover the whole spectrum of oblique extension. They are conducted using an elasto-visco-plastic finite element model and involve crustal and mantle layers accounting for self-consistent necking of the lithosphere. … Read more…

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Geochemistry, Geophysics, Geosystems – Evolution of stress and fault patterns in oblique rift systems: 3-D numerical lithospheric-scale experiments from rift to breakup

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Brune, S. (2014). Evolution of stress and fault patterns in oblique rift systems: 3‐D numerical lithospheric‐scale experiments from rift to breakup. Geochemistry, Geophysics, Geosystems, 15(8), 3392-3415. doi: 10.1002/2014GC005446.

Evolution of stress and fault patterns in oblique rift systems: 3‐D numerical lithospheric‐scale experiments from rift to breakup

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EarthByte Group makes the finals of the Eureka Prize

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The EarthByte group is a finalist for the Eureka Prize from the Australian Museum, for its development of GPlates software! The prize is awarded annually for research innovation and GPlates was nominated for providing a “experimental virtual planet” to investigate geological systems through deep time. You can read more about the Eureka Prize here. Watch the … Read more…

Solid Earth – Pacific plate slab pull and intraplate deformation in the early Cenozoic

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Butterworth, N. P., Müller, R. D., Quevedo, L., O’Connor, J. M., Hoernle, K., & Morra, G. (2014). Pacific Plate slab pull and intraplate deformation in the early Cenozoic. Solid Earth, 5(2). doi: 10.5194/se-5-757-2014. Pacific Plate slab pull and intraplate deformation in the early Cenozoic

Plate reconstructions of Southeast Asia

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This animation is from our recent work on Southeast Asian plate reconstructions.Read the peer-reviewed paperCitationZahirovic, S., M. Seton, and R. Müller (2014), The Cretaceous and Cenozoic tectonic evolution of Southeast Asia, Solid Earth (EGU), 5, 227-273. doi: 10.5194/se-5-227-2014.View similar animations on our EarthByte YouTube channel

Continental rifting in 3D using Underworld

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This model shows the evolution of a continental rift from inception to breakup, using the Underworld numerical modelling framework. The left and right walls of the model are pulled apart from each other at a total rate of 2 cm/yr to induce rifting.Courtesy of Luke Mondy, EarthByte.View other EarthByte animations on our YouTube channel

EarthByte welcomes Mike Tetley

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Welcome back to Mike Tetley, who has commenced a PhD with EarthByte this week, under the supervision of Dietmar Müller, Simon Williams, Nico Flament and collaborator, Mike Gurnis at CalTech. Mike is a recipient of a University of Sydney Merit Award from his Honour’s degree study which focused on palaeomagnetics of the Palaeozoic Lachlan Orogen.

Nature Communications – Rift migration explains continental margin assymetry and crustal hyper-extension

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Brune, S., Heine, C., Pérez-Gussinyé, M., & Sobolev, S. V. (2014). Rift migration explains continental margin asymmetry and crustal hyper-extension. Nature communications, 5. doi: 10.1038/ncomms5014. Rift migration explains continental margin asymmetry and crustal hyper-extension Download supplementary information – pdf

Rift migration explains continental margin asymmetry and crustal hyper-extension

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Rift MigrationWhen continents break apart, continental crust and lithosphere are thinned until break-up is achieved and an oceanic basin is formed. The most remarkable and least understood structures associated with this process are up to 200 km wide areas of hyper-extended continental crust, which are partitioned between conjugate margins with pronounced asymmetry. Here we show, using high-resolution thermo-mechanical modelling, that hyper-extended crust and margin asymmetry are produced by steady state rift migration. … Read more…

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Integrating deep-Earth and surface processes for frontier-basin exploration

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Project Summary
Sea level has changed by up to 300m through geological time. These fluctuations, caused by plate tectonics and convection in the Earth’s mantle, have created vast sedimentary basins and associated resources such as petroleum, natural gas and coal.

In this project, we propose to bring together global 4D databases with cutting-edge 3D numerical simulations to reconstruct how mid-ocean ridge creation and the recycling of old, cold oceanic plates into the mantle have driven surface topography and sea-level change globally since the breakup of the super-continent Pangaea. … Read more…

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Gondwanaland extension, breakup and continental margin evolution

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Project Summary
Plate reconstruction models for the rifting and separation of Gondwanaland’s conjugate margins continue to be poorly constrained in detail. We propose to develop a new plate model for the entire Indian ocean by synthesizing old and new geological and geophysical data using our plate tectonic software system. We will test continental fit reconstruction hypotheses and alternative models for the early opening of the Indian Ocean by using a variety of reconstructed gridded and vector data sets.  … Read more…

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Earth and Planetary Science Letters – Burial and exhumation during Archean sagduction in the East Pilbara Granite-Greenstone Terrane

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François, C., Philippot, P., Rey, P., & Rubatto, D. (2014). Burial and exhumation during Archean sagduction in the East Pilbara granite-greenstone terrane. Earth and Planetary Science Letters, 396, 235-251. doi: 10.1016/j.epsl.2014.04.025. Burial and exhumation during Archean sagduction in the East Pilbara granite-greenstone terrane Supplementary information is available from Science Direct here Download the combined supplementary tables … Read more…

Solid Earth – The Cretaceous and Cenozoic tectonic evolution of Southeast Asia

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Zahirovic, S., Seton, M., & Müller, R. D. (2014). The Cretaceous and Cenozoic tectonic evolution of Southeast Asia. Solid Earth, 5(1), 227-273. doi:10.5194/se-5-227-2014. The Cretaceous and Cenozoic tectonic evolution of Southeast Asia Download supplementary material – zip file

GPlates 1.4 now available to download

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GPlates Version 1.4 has been released! This latest update of GPlates brings added functionality for the export of both numerical floating point-data and colour reconstructed rasters, for a user specified region and resolution. There is also greater flexibility for raster file import, with ERMapper, Erdas Imagine and GeoTIFF files now supported and geo-referencing is retained … Read more…