Permian-Triassic Boundary: a tyro's view

Abstract

The major stratigraphic divisions of the Phanerozoic are based on "mass extinction events", a concept that is gradually losing followers. These divisions are called systems, and the boundaries between the different systems are often arbitrarily drawn. In continuous sequences, it is usually possible to clearly draw the system boundaries, but in case of global stratigraphic gaps, as between the Permian and the Triassic, the placement of the system boundary becomes a difficult task. This paper discusses and analyses information available on the Permian-Triassic transition, both in marine and non-marine sequences, and brings out gaps in information. It has been suggested that the system boundaries are not natural boundaries, and hence instead of focusing on a static PTB, that is, on an abrupt change from Permian to Triassic, more emphasis should be placed on the transition from Permian to Triassic which may be referred to as the PTB Interval.