Aptian ammonite of the Sallah Formation, central Saudi Arabia
Résumé
The Sallah Formation crops out in Central Saudi Arabia where it is 30 meters thick. It consists of lagoonal and inter-tidal sediments, including locally a marine fauna, which were deposited during a regional trangression above the Biyadh Sandstone. The formation is unconformably overlain by the continental clastics of the Huraysan Formation. A single ammonite recovered from the Sallah Formation is here conclusively assigned to the top of Lower to base of Upper Aptian Cheloniceras sp. and supports its correlation to the Early Aptian Shu'aiba Formation in the subsurface of eastern Saudi Arabia. The Sallah Formation forms a complete transgressive-regressive sequence and the middle Sallah unit 2 (11 meters thick) contains the maximum flooding surface MFS K80. The Late Aptian, for the most part, is interpreted as a hiatus of non-deposition associated with a major sea-level lowstand in Central Saudi Arabia. The overlying continental Huraysan Formation is correlated to the Nahr Umr Formation of Oman and the United Arab Emirates and Burgan Formation of Kuwait.