Abstract by author:
A new theory, for the deposition of the Irati and Whitehill Shale Formations and for the outline of the connection between the Parana (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