First Record of Conodonts from the Permo-Triassic Khartam Member, Khuff Formation in Central Saudi Arabia

Abstract

<p>The Permo-Triassic boundary has been proposed to lie between the upper and lower Khartam Members of the Khuff Formation in central Saudi Arabia. Earlier studies relied on sequence stratigraphy and geochemistry as tools for identifying the Permo- Triassic boundary. This resulted in placing the boundary in different stratigraphic positions. Worldwide, conodonts are known to be the best indicators for defining the Permo-Triassic boundary biostratigraphically. In this study, we discovered two lithological units containing conodonts in different stratigraphic positions in the Khartam Member. Conodonts in the lower stratigraphic unit were recovered from calcareous silty mudstone, while conodont samples from the upper stratigraphic unit were recovered from calcareous siltstone. Thin section petrography initially revealed the conodonts, while XRF, XRD, SEM, and QEMSCAN techniques were used to confirm the presence of biogenic apatite. Conodonts collected from the two stratigraphic intervals of the Khartam Formation showed distinct and different morphological features. Conodonts of the lower unit mainly belong to the Neogondolellids group, while conodonts from the upper unit belong to the Anchignathodontids group. This new discovery represents the first step for a clear definition of the Permo-Triassic boundary in the Arabian Peninsula.  </p>