Biostratigraphy and evolution of larger rotaliid foraminifera in the Cretaceous–Palaeogene transition of the southern Oman Mountains

Abstract

A site in the western flank of Jabal Ja’alan (Oman Mountains) reveals an exceptional succession across the Cretaceous–Palaeogene boundary. The sampled interval comprises a series of carbonates deposited in shallow-water platform environments and belonging to the Murka Formation, which lies between the Simsima and Abat formations of latest Cretaceous and Thanetian age, respectively. The larger foraminifera recovered from this interval belong essentially to the group of larger rotaliids (Rotaliidae). Two new genera and two new species are here described, Praelockhartia neoakbari gen. et sp. nov. and Rotaliidium parvum gen. et sp. nov. The former shows a very characteristic architecture of an umbilicus with strong piles and two types of umbilical cavities, while the latter has characteristic dorsal supplementary chamberlets. Other species such as Rotalia cf. jacobi, Rotorbinella hensoni, Rotospirella conica and Lockhartia sp. complete the rotaliid assemblage. The entire assemblage can be considered to be of late Danian age and to belong to shallow benthic zone SBZ 2. The larger rotaliids appear to have recovered and diversified earlier than any other larger benthic foraminifera in the region after the K–Pg crisis. The rotaliids from the Murka Formation also appear to be linked to the Lockhartiinae and to play a special role in improving our understanding of subsequent diversification in the Lockhartia Sea. A new subfamily, Praelockhartiinae, is erected to accommodate all primitive forms that are architecturally close to lockhartiines. Key words: Foraminifera, Rotaliidae, Maastrichtian, Danian, Paleocene.

A site in the western flank of Jabal Ja’alan (Oman Mountains) reveals an exceptional succession across the Cretaceous–Palaeogene boundary. The sampled interval comprises a series of carbonates deposited in shallow-water platform environments and belonging to the Murka Formation, which lies between the Simsima and Abat formations of latest Cretaceous and Thanetian age, respectively. The larger foraminifera recovered from this interval belong essentially to the group of larger rotaliids (Rotaliidae). Two new genera and two new species are here described, Praelockhartia neoakbari gen. et sp. nov. and Rotaliidium parvum gen. et sp. nov. The former shows a very characteristic architecture of an umbilicus with strong piles and two types of umbilical cavities, while the latter has characteristic dorsal supplementary chamberlets. Other species such as Rotalia cf. jacobi, Rotorbinella hensoni, Rotospirella conica and Lockhartia sp. complete the rotaliid assemblage. The entire assemblage can be considered to be of late Danian age and to belong to shallow benthic zone SBZ 2. The larger rotaliids appear to have recovered and diversified earlier than any other larger benthic foraminifera in the region after the K–Pg crisis. The rotaliids from the Murka Formation also appear to be linked to the Lockhartiinae and to play a special role in improving our understanding of subsequent diversification in the Lockhartia Sea. A new subfamily, Praelockhartiinae, is erected to accommodate all primitive forms that are architecturally close to lockhartiines. Key words: Foraminifera, Rotaliidae, Maastrichtian, Danian, Paleocene.

A site in the western flank of Jabal Ja’alan (Oman Mountains) reveals an exceptional succession across the Cretaceous–Palaeogene boundary. The sampled interval comprises a series of carbonates deposited in shallow-water platform environments and belonging to the Murka Formation, which lies between the Simsima and Abat formations of latest Cretaceous and Thanetian age, respectively. The larger foraminifera recovered from this interval belong essentially to the group of larger rotaliids (Rotaliidae). Two new genera and two new species are here described, Praelockhartia neoakbari gen. et sp. nov. and Rotaliidium parvum gen. et sp. nov. The former shows a very characteristic architecture of an umbilicus with strong piles and two types of umbilical cavities, while the latter has characteristic dorsal supplementary chamberlets. Other species such as Rotalia cf. jacobi, Rotorbinella hensoni, Rotospirella conica and Lockhartia sp. complete the rotaliid assemblage. The entire assemblage can be considered to be of late Danian age and to belong to shallow benthic zone SBZ 2. The larger rotaliids appear to have recovered and diversified earlier than any other larger benthic foraminifera in the region after the K–Pg crisis. The rotaliids from the Murka Formation also appear to be linked to the Lockhartiinae and to play a special role in improving our understanding of subsequent diversification in the Lockhartia Sea. A new subfamily, Praelockhartiinae, is erected to accommodate all primitive forms that are architecturally close to lockhartiines. Key words: Foraminifera, Rotaliidae, Maastrichtian, Danian, Paleocene.