The Tambien Group, Northern Ethiopia (Tigre)

The Tambien Group of northern Ethiopia (Tigre), with probable correlatives in Eritrea, is a 2-3-km-thick siliciclastic-carbonate succession that was deposited in an intra-oceanic arc platform setting within the southern Arabian-Nubian Shield (ANS) area (southern extension of the Nakfa Terrane) of the Mozambique Ocean. Its deposition occurred prior to ocean closure between converging fragments of East and West Gondwana and concomitant structural emergence of the East African Orogen (EAO). The Tambien Group is well exposed and best studied in the Mai Kenetal and Negash synclinoria, where litho- and chemostratigraphy (including δ ¹³C _carb, ⁸⁷Sr/ ⁸⁶Sr) provide the basis for a composite reference section. Two glaciogenic intervals have been suggested from exposures within the Didikama and Matheos Formation in the Negash Synclinorium. No reliable palaeomagnetic data exist to constrain the palaeolatitude of Tambien Group deposition and the southern ANS, but palaeogeographic reconstructions and evaporite pseudomorphs in lower carbonate units (Didikama Formation) imply low to intermediate latitudes (<45°). Integration of available geochronological information (regional magmatism and detrital zircon) suggests c. 775-660 Ma as a plausible window constraining deposition of the prospective glacial intervals.