A period of marine transgression coincides with the time of the Permian-Triassic Boundary. (Hallam, 2000) This transgression can be seen in many Permian-Triassic sections worldwide and is typified by a decrease in thickness and abundance of storm beds coupled with a general decrease in grain size. Generally, this transgression appears to have coincided with, and perhaps caused, the spread of oxygen-poor bottom waters over the shallow shelves of Pangaea. The extent and duration of this event was a significant factor in delaying the post end-Permian extinction recovery (Twitchett, 2003)