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.
Late Eocene to Early Oligocene Calcareous Nannofossil Assemblages from Sites 699 and 703, Subantarctic South Atlantic Ocean
