Cees Passchier, University of Mainz
Orogenic triple junctions between mobile belts usually form in two unrelated stages by subsequent and oblique continental collisions separated by a significant time span. Besides these “oblique triple junctions” another type, named “transverse triple junctions”, may exist. Such junctions are created by a more complex mechanism of partly contemporaneous convergence of three cratons in a restricted time frame, involving strike slip.
The Neoproterozoic‒Cambrian Kaoko-Damara junction between the Rio de la Plata, Congo, and Kalahari cratons in Namibia is an example of such a transverse orogenic triple junction, formed by at least four subsequent but partly related deformation events. Initial north-south convergence between the Congo and Kalahari cratons was followed by east-west collision of the Rio de la Plata and Congo cratons. Subsequently, the Kalahari and Congo cratons collided, contemporaneous with sinistral strike-slip motion between the Congo and Rio de la Plata cratons and with the intrusion of granite-syenite plutons.
The Namibian triple junction has been reconstructed by detailed field mapping of up to five overprinting foliations in low grade metaturbidites. Besides their use in the reconstruction of large scale tectonics, these foliations show a number of unusual settings. Most interesting are “sector foliations”, which do not overlap but fill adjacent space, and “flame foliations”, foliations that form in extension rather than shortening.
|Date||Wednesday, 7 March 2018|
|Time||1:00pm - 2:00pm|
|Location||Benson Common Room (Gn9), Geology Building, 360 Leith Street, Dunedin|