Mechanisms and timescale of West Gondwana amalgamation
The supercontinent Gondwana formed in a sequence of orogenic episodes between 800 and 500 million years ago as a result of the break-up of the supercontinent Rodinia and reconfiguration of its cratonic fragments during opening and closure of new oceans. Neoproterozoic orogens of West Gondwana are today dispersed in South America and Africa separated by the Atlantic Ocean. Amalgamation of three or more cratons and potential microplates or terranes led to a complex array of highly oblique and locally intersecting mobile belts at the triple points of collision. Plate-tectonic reconstructions of West Gondwana assembly and cross-border and cross-ocean correlations of orogenic belts are still controversial due to uncertain number and origin of involved terranes, unknown occurrence and width of former oceanic basins, along-strike variations in geometry, kinematics, metamorphism and magmatism within mobile belts, timing of accretionary or collisional events, and number and polarity of subduction zones. Particular the processes acting during contemporaneous collision of three cratons and the nature of the resulting orogenic zones is little understood in detail. A lot of new data have been gathered during the last years. We invite contributions discussing the time-frame, mechanisms and structural elements of orogens related to West Gondwana amalgamation from a geological, geochemical, and geophysical perspective.
Kerstin Saalmann and Jeremie Lehmann