Upper Eocene planktonic foraminifera from northern Saudi Arabia: implications for stratigraphic ranges

Abstract

Abstract. The Rashrashiyah Formation of the Sirhan Basin in northern Saudi Arabia contains diverse assemblages of planktonic foraminifera. We examined the biostratigraphy, stratigraphic range and preservation of upper Eocene planktonic foraminifera. Assemblages are well-preserved and diverse, with 40 species and 11 genera. All samples are assigned to the Priabonian Globigerinatheka semiinvoluta Highest Occurrence Zone (E14), consistent with calcareous nannofossil biostratigraphy indicating Zone CNE17. Well-preserved planktonic foraminifera assemblages from the lower part of the upper Eocene are rare worldwide. Our study provides new insights into the stratigraphic ranges of many species. We find older (Zone E14) stratigraphic occurrences of several species of Globoturborotalita previously thought to have evolved in the latest Eocene (Zone E15, E16) or Oligocene; these include G. barbula, G. cancellata, G. gnaucki, G. pseudopraebulloides, and G. paracancellata. Older stratigraphic occurrences for Dentoglobigerina taci and Subbotina projecta are also found, and Globigerinatheka kugleri occurs at a younger stratigraphic level than previously proposed. Our revisions to stratigraphic ranges indicate that the late Eocene had a higher tropical–subtropical diversity of planktonic foraminifera than hitherto reported.

Calcareous nannofossils across the Eocene-Oligocene transition at Site 756 (Ninetyeast Ridge, Indian Ocean): implications for biostratigraphy and paleoceanographic clues

“…4., Figs. 1-3) and H. primitiva only, are scarce and the Turborotalita cerroazulensis-cunialensis group, common elsewhere in the tropics and sub-tropics (Nocchi et al 1986, Katz et al 2008, Edgar et al 2020, Wade et al 2021) is virtually absent. The less angular/more globular relatives Turborotalita ampliapertura and T.…”

Spine-like structures in Paleogene muricate planktonic foraminifera

“…The muricate group suffered a major extinction shortly before the end of the middle Eocene, at which time Morozovelloides and large Acarinina became extinct in quick succession (Wade, 2004;Wade et al, 2012). Small acarininids with the characteristic spinose muricate wall survived into the late Eocene and early Oligocene, but only at low diversity and abundance (Wade and Hernitz Kucenjak, 2018;Wade et al, 2021). The "modern"-style taxonomic and ecological order of planktonic foraminiferal assemblages developed throughout the Miocene as the spinose Globigerinoidea refilled many of the ecological niches left vacant by the muricates, albeit with a substantial intervening time gap.…”