Upper Cretaceous to Lower Eocene calcareous nannofossil biostratigraphy from Malaqet and Mundassah sections western flank of the Northern Oman Mountains

Abstract

This work is the first attempt to undertake a biostratigraphic study on calcareous nannofossil assemblages of the exposed Upper Cretaceous to Lower Eocene rocks at the Malaqet and Mundassah sections, NW Oman. The Upper Cretaceous to Lower Eocene rocks belong to the Simsima Formation and the Muthaymimah Formation. Specimens of calcareous nannofossils identified during this study have been ascribed to 67 different species. The Cretaceous/Palaeocene boundary can be placed in correspondence with the unconformity between the mentioned formations. The presence of a big hiatus in this area is suggested by the absence of the latest Maastrichtian Micula prinsii nannofossil Zone, and the Palaeocene NP1 and NP2 nannofossil Zones. In the two study sections, the Danian/Selandian boundary is placed at the level of the first occurrence (FO) of Fasciculithus tympaniformis (base of NP5 Zone).At Jabal Mundassah, the Selandian/Thanetian boundary is positioned at the FO of Discoaster mohleri, which is used to define the base of NP7/8 Zone. Unfortunately, a major hiatus is detected at the Selandian/Thanetian boundary at the Jabal Malaqet section as indicated by the absence of NP6 and NP7/8 Zones. The Paleocene/Eocene boundary is placed at the base of Subzone NP9b at Jabal Mundassah, whereas at Jabal Malaqet the Paleocene/Eocene boundary interval is missing and a major hiatus is testified by the absence of the NP9b Subzone and NP10 Zone. This work is the first attempt to undertake a biostratigraphic study on calcareous nannofossil assemblages of the exposed Upper Cretaceous to Lower Eocene rocks at the Malaqet and Mundassah sections, NW Oman. The Upper Cretaceous to Lower Eocene rocks belong to the Simsima Formation and the Muthaymimah Formation. Specimens of calcareous nannofossils identified during this study have been ascribed to 67 different species. The Cretaceous/Palaeocene boundary can be placed in correspondence with the unconformity between the mentioned formations. The presence of a big hiatus in this area is suggested by the absence of the latest Maastrichtian Micula prinsii nannofossil Zone, and the Palaeocene NP1 and NP2 nannofossil Zones. In the two study sections, the Danian/Selandian boundary is placed at the level of the first occurrence (FO) of Fasciculithus tympaniformis (base of NP5 Zone).At Jabal Mundassah, the Selandian/Thanetian boundary is positioned at the FO of Discoaster mohleri, which is used to define the base of NP7/8 Zone. Unfortunately, a major hiatus is detected at the Selandian/Thanetian boundary at the Jabal Malaqet section as indicated by the absence of NP6 and NP7/8 Zones. The Paleocene/Eocene boundary is placed at the base of Subzone NP9b at Jabal Mundassah, whereas at Jabal Malaqet the Paleocene/Eocene boundary interval is missing and a major hiatus is testified by the absence of the NP9b Subzone and NP10 Zone.

Keywords

• Jabals: Malaqet- Mundassah- Calcareous Nannofossils- Simsima Formation- Muthaymimah Formation – Upper Cretaceous-Paleocene- Eocene- Biostratigraphy.