Proterozoic sedimentary basins within the Southern East African Orogen: A gondwana link

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Collins, Alan۱; Kinny, Peter۲; Santosh, M۳; Razakamanana, Theodore۴; Clark, Chris۲
Holding Date 05 October 2008

Many metasedimentary rocks are caught up in the southern East African Orogen that in a reconstructed Gondwana lay along an across-orogen transect from Tanzania, through Madagascar into southern India. Detrital zircons from these metasedimentary rocks, and the ages of crosscutting igneous intrusions demonstrates that there are two voluminous depositional age rock packages. The oldest are late Palaeoproterozoic to early Mesoproterozoic quartzites, pelites and carbonates that in central Madagascar are called the Itremo Group. These sedimentary rocks are sourced from NeoArchaean and Palaeoproterozoic sources and can be traced into southern Madagascar where they make up much of the Androyen Series, and into the southeast of the Madurai Block of India. A second, younger, period of deposition is marked by the Ediacaran deposition of the Molo Group in central Madagascar, the volcanosedimentary Vohibory series of southern Madagascar, Neoproterozoic sedimentary rocks within the Achancovil zone of southern India and possibly the protoliths to north-eastern Tanzania, southeastern Kenya.
In this presentation we shall document the evidence for the existence of two major periods of deposition of rocks now caught up within the southern East African Orogen, discuss their palaeogeographic distribution, point out the constraints they place on the tectonic evolution of the region and show how they help link-up this central part of Gondwana.