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Geological Society, London, Special Publications; 1990; v. 49; p. 189-202;
DOI: 10.1144/GSL.SP.1992.049.01.12
© 1990 Geological Society of London

Evolution of the Oman Tethyan Continental Margin

Evolution of the Triassic Hawasina Basin, Central Oman Mountains

D. Bernoulli1, H. Weissert1 & C. D. Blome2

1 Geology Institute, ETH-Zentrum, CH-8092 Zurich, Switzerland
2 United States Geological Survey, Denver, Colorado 80225, USA

Sediments of Late Triassic age preserved in the upper Hawasina nappes of the Central Oman Mountains document the early sedimentary and oceanographic evolution of a segment of the Triassic seaway bordering the northern Gondwanian continental margin. Within the Zulla Formation of Glennie et al. four members can be distinguished.

4. Halobia limestones (Lower to ?Upper Norian)
3. Radiolarian cherts (Ladinian to Lower Norian)
2. Sandstone-shale member
1. Calcarenite-shale member

Changes in composition and abundance of turbiditic sediments in the Zulla Formation reflect environmental changes in the source areas, probably linked to sea-level fluctuations, whereas changes in the pelagic facies reflect basin-wide oceanographic fluctuations. Episodic low-oxygen conditions are indicated by laminated dolomites in the calcarenite-shale member. An increase in radiolarian abundance may record an increase in surface-water productivity possibly related to a sea-level rise and corresponding changes in the circulation pattern. A deepening of the CCD during the Early Norian is documented by the Halobia limestones. Similar facies types are encountered along the South-Tethyan seaway (Lagonegro-Pindos-Antalya-Pichakun). However, diachroneity of facies changes from radiolarite to limestone point to differences in the bathymetric and/or oceanographic evolution of the basins.