Campanian–Maastrichtian unconformities and rudist diagenesis, Aruma Formation, central Saudi Arabia
Özer, Sacit . 2019
Abstract
The Upper Cretaceous Aruma Formation is widely distributed in central Saudi Arabia and consists of three members, from base to top, the Khanasir Limestone Member, the Hajajah Limestone Member, and the Lina Shale Member. It disconfomably overlies
the CenomanianWasia Formation (middle Turonian, the BWasia-Aruma break^). Two unconformities were recorded within and at the top of the Aruma Formation: (a) Bthe lower Campanian unconformity^ between the Khanasir Limestone Member and the
Hajajah Limestone Member and (b) Bthe pre-Cenozoic unconformity^ between the Lina Shale Member and the Paleogene Ummer Radhuma Formation. The comparison between these unconformities and those recorded on the Arabian Plate was emphasized. A lenticular rudist biostrome in the uppermost part of the Khanasir Limestone Member consists mainly of the radiolitids and sparse canaliculated rudists in life position. However, rudists are entirely fragmented in the lower limestone and are very rare in the upper limestone of the Hajajah Limestone Member. Loose right valves of radiolitids from the Campanian Khanasir Member have underwent diagenetic alterations, such as fragmentation and compaction, micritization, bioerosion, and micritic calcite cement, which indicates marine diagenetic stage, while very limited silicification, dolomitization, and dissolution suggest the
meteoric diagenetic environments with arid climates. Isopachus and equant calcite cement and neomorphism may be showed the fresh pharetic zone related with subaerial unconformities
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