Triassic ammonoids from Jabal Safra and Wadi Alwa, Oman, and their significance

Abstract

Abstract Triassic ammonoids are recorded from Jabal Safra and Wadi Alwa, Oman. Most or all are from olistoliths. The ammonoids from Jabal Safra are of Early Triassic (Smithian and Spathian) age and are from metre-sized blocks in the Jurassic Guwayza Formation. Those from Wadi Alwa are from blocks ranging from metre- to more than decimetre-size and are Early Triassic (Smithian and Spathian), Middle Triassic (Anisian) and Late Triassic (Norian). The Early and Middle Triassic ammonoids from both localities are in dense, highly fossiliferous, commonly red limestone where they occur to the exclusion of all other macrofossils. The facies is that of the Hallstatt Limestone which is known from many localities, all in the Tethys. The Late Triassic ammonoids are in a red argillaceous limestone like the Ammonitico Rosso, another characteristic facies in Tethys. The occurrences at Jabal Safra are in the Hawasina allochthon. The olistoliths evidently came from the east, not from the platform to the west. Seamounts east of the main Hawasina depocentre seem the most likely source for all the Triassic blocks.