Palaeogeography and sedimentation models for the Whitehill-Irati sea during the Permian of South America and southern Africa

Sammanfattning: The endemic mesosaurid reptiles of the Whitehill-Irati sea in southern Africa and South America during the Permian were studied with preference for the Namibian material. To date three valid mesosaurid species have been described of which two occur on both continents. These mesosaurid aquatic reptiles were among the first evidence used to support the theory of continental drift at the beginning of this century. A new theory, for the deposition of the Irati and Whitehill Shale Formations and for the outline of the connection between the Paraná (South America) and the Karoo basins (southern Africa) during the deposition of the two formations, is presented. Marine conditions prevailed in the Whitehill-Irati sea during Upper Dwyka times but turned into brackish before the deposition of the Irati and Whitehill Shale Formations probably due to crustal instability at the southern margins of the basins. A silled basin developed and anoxic bottom conditions appeared as a result of the restricted water circulation and stratification of the water body.