Significance of Upper Jurassic Sediments in the Knysna Outlier (Cape Province)

Abstract

DR DINGLE replies: Dr Jones's stressing of whether the commencement of the formation of the eastern Agulhas Bank dates from the time of rifting or drifting between East and West Gondwana is something of a red herring. As the Agulhas Bank consists of a thick Mesozoic sediment wedge built onto a block-faulted Palaeozoic basement, the age of initiation of the construction of this wedge dates from the first sediments deposited onto the down-faulted basement. These sediments are at least as old as lower Upper Jurassic. The fact that the sediments deposited in the Knysna area during Upper Jurassic times were paralic in nature is also not significant, as it happens. Knysna lay at the northern limit of the Jurassic–Lower Cretaceous sea—it lies in a similar position today—and shallow marine sediments with interfingering lagoonal/terrestrial beds are precisely what one would expect from the establishment of an ocean adjacent to the area.