Since the recent publication (Reeves, C.V., 2018: Petroleum Geoscience, vol 24, pp 41-56) there have been several significant refinements to the model of Gondwana dispersion. Many of these have been made in the last six months. Model CR19ABDJ, incorporating them, is demonstrated in the animation above. Precambrian terranes that made up Gondwana are shown in pink. In forward time, the growth of the oceans between them is depicted with the movement of the mid-ocean ridges (red with grey transforms) in relation to the mantle plumes (yellow ticks), the creation of the large igneous provinces (blue) and the pattern of fracture zones now evident in the topogprahy of the ocean floor (pale blue). The animation also runs in reverse to illustrate how the features of the ocean floor make the interpretation possible. The aimation is made from frames at intervals of 5 myr from 0 to 185 Ma and at 10 myr intervals 190 to 300 Ma. The Atlas software of CPSL was used throughout. Research updates describing the recent work appear in Section 4 (follow the link under heading 4 below). Look out for more updates soon.
2019 May 3
Contents of this Section
1. An Introduction to the Principles of Global Tectonics [click here] - for the non-specialist.
2. References [click here] - published work as well as the ‘grey’ literature for the specilaist.
3. A 12-Lecture Course on Gondwana Geodynamics [click here] - for those who want to learn.
4. Global Thoughts [click here] - latest Research Updates with recent ideas for discussion.
The core of the work over many years has been the quest for a rigorous geometrical model for the re-assembly and dispersal of the whole of Gondwana. The model comprises a series of Euler interval poles for the plate circuit Madagascar -> Africa -> Antarctica -> India that are available on request. 'Atlas' software from Cambridge Paleomap Services (CPSL) has been the workbench for all these efforts. Insights gained from hands-on experience with the geological reconnaissance through geophysical mapping of many whole countries in eastern and southern Africa, as well as India and Australia, 1970-2018, is brought to bear wherever possible. The work forms part of IGCP-628, the Geological Map of Gondwana [link to IGCP-628].
Much of the Gondwana continent can still be found preserved as rigid Precambrian crustal fragments (shown in pink) that have retained the same size and shape that they had within unified Gondwana at the end of Precambrian times. In the reassembly they are separated by an estimated amount of continental crust that has since been stretched in rifting processes and lost from view below Phanerozoic cover in rift zones and continental margins. Igneous rocks related to the activity of the labelled mantle plumes - mostly large volcanic plateaus in the oceans - are shown in blue.
Active mid-ocean ridges are shown in red with major transforms in dark grey and extinct ridges dashed in black. Plume loci in a fixed mantle reference frame are shown as yellow circles (initially 1000 km in diameter) in the forward animation. Rifting within Africa is indicated in a somewhat stylised way, Karoo (Permian-Triassic) in orange, Cretaceous rifting in green and the current East Africa rifting in yellow. Karoo deposits, pre-dating Gondwana dispersal, are shown in pale orange and Cenozoic and younger cover in yellow. The animation supercedes that of model CR18ABHG which is described in Reeves (2018). The latest developments are explained in the Research Updates (Section 4 above).
What you see at the top of this page is an animated GIF file about 6 Mb in size. By right-clicking on the image and saving it to your computer it may then be imported as a video into a Powerpoint presentation, for example. The images and the animations are free for teaching or research purposes, with suitable acknowledgment. Please seek permission for commercial use. Enquiries and suggestions for collaborative studies are always welcome.
A series of 41 JPG images to accompany an earlier animation has been generated at higher resolution. These images show the ocean crust in colour, based loosely (and with permission) on the CGMW Geological Map of the World (2010). [Ref: Geological Map of the World, 3rd edition, scale 1 :25 000 000. Ph. Bouysse et coll. © CCGM-CGMV / 2010. www.ccgm.org]. Model CR16ABCL was used in May 2016 to generate a series of maps in equatorial equidistant projection that may be accessed here.
2019 May 3