Pre- and syn-orogenic sedimentation and volcanic activity in the internal domain of the southern Kaoko–Dom Feliciano–Gariep orogenic system

Abstract

This work discusses the timing and sources for the pre- and syn-orogenic sedimentation in the southernmost internal domain of the Kaoko–Dom Feliciano–Gariep orogen. One sample from the Marmora Terrane (Gariep Belt, southern Namibia) yielded data suggesting a syn-orogenic origin, whereas data from two other samples suggest their pre-orogenic nature. Two volcanic rocks from the San Carlos Formation (Punta del Este Terrane, Uruguay) yielded U–Pb zircon and monazite ages of 578 ± 7 and 562 ± 7 Ma, respectively, providing the timing of sedimentation, whereas U–Pb detrital zircon data confirm the syn-orogenic origin of the basin. Two Tonian metavolcanic rocks from the Coastal Terrane (Kaoko Belt, Namibia), considered an analogue of the now eroded supracrustal part of the Punta del Este Terrane, were analysed for Hf isotopes. The results of the U–Pb dating and Hf isotopic analysis of all the samples are compared with the data from other geological units in the Gariep and southernmost Dom Feliciano belts and discussed with respect to the model of rifting-related origin of the Kaoko–Dom Feliciano–Gariep orogenic hinterland, as well as to the currently recognized two-stage orogenic evolution in this part of the former southwestern margin of Gondwana.