This note discusses the lithostratigraphic nomenclature used to characterise the Permian–Triassic
transition at outcrop in the Oman Mountains, with emphasis on the position of the boundary
between the Saiq and Mahil formations. Two inconsistent criteria for picking the Saiq/Mahil
Boundary (SMB) prevail in the literature causing confusion regarding the correct position of the
Permian/Triassic Boundary (PTB). The position of the PTB plays a central role in the correlation of
these two formations from outcrop to the subsurface Khuff and overlying Sudair formations.
The Khuff Formation contains one of the world’s greatest reserves of non-associated gas, and
its outcrop equivalent in the Oman Mountains is increasingly being studied for the purposes of
regional correlations, reservoir characterisation and exploration. Therefore an agreement on the
position of the SMB is a pre-requisite for precise communication among geoscientists. In this note we
review the historical source of the confusion and recommend applying stratigraphic rules to resolve
the position of the Saiq/Mahil Boundary (SMB).