Planktic foraminiferal biostratigraphy of the Oligocene–Pliocene successions in the offshore well A1-89, Sirt Basin, Libya

This study deals with planktic foraminiferal biostratigraphy of the Oligocene-Pliocene successions in the offshore Well A1-89 of the Sirt Basin. One hundred and forty-one ditch cutting samples covering the interval from 1050ft to 9000ft have been analyzed for this study. Fifty-five planktic foraminifera taxa belonging to seventeen genera have been identified. Ten planktic foraminiferal biozones have been recognized herein based on the integration of Bolli and Saunders’s (1985), Berggren et al.(1995), Steininger et al. (GSSP 1997), and Wade et al. (2011), zonal schemes. In descending order, they are Sphaeroidinellopsis seminulina (Zanclean-Piacenzian); Praeorbulina sicana (Burdigalian-Langhian); Globigerinoides bisphericus (Burdigalian); Globigerinatella sp./Catapsydrax dissimilis (Burdigalian); Globigerinoides primordius (Aquitanian); Paragloborotaliakugleri (Aquitanian); Globigerinaciperoensis ciperoensis (Chattian);Globorotalia opima opima (Chattian); Globigerina ampliapertura (Rupelian);Cassigerinella chipolensis/Pseudohastigerina micra (Rupelian). The Oligocene/Miocene boundary is found to be conformable and placed at the top of the Globigerina ciperoensis ciperoensis Biozone. However, the Miocene/Pliocene boundary is unconformable and placed at the top of the Praeorbulina sicana Biozone. Additionally, the established biozones have been regionally correlated with their equivalents in Tunisia and Egypt.