Master Thesis Planktonic Foraminiferal Biostratigrahy of the Oligocene-Pliocene Succession in the Offshore Well A1-89, Sirt Basin, Libya

Abstract

The present study deals with Oligocene-Pliocene planktonic foraminiferal biostratigraphy of the studied succession at Well-A1-89 in the offshore of Sirt Basin. One hundred and forty one ditch cutting samples have been used for this study, covering the interval from 1050’ – 9000’. The examination of the studied samples has led to the identification of fifty-one species and eleven subspecies belong to twelve genera. On the basis of the vertical stratigraphic distribution of the planktonic foraminiferal species, with particular attention to last occurrence (LO) of the marker species, ten planktonic foraminiferal biozones have been identified through the studied succession following Bolli and Saunders (1985) and Iaccarino (1985) zonal schemes, in descending order as follows: Sphaeroidinellopsis seminulina s.l (Zanclean); Praeorbulina glomerosa (Langhian); Globigerinoides trilobus (Burdigalian); Catapsydrax dissimlis (Aquitanian-Burdigalian); Globigerinoides primordius (Aquitanian); Globorotalia kugleri (Chattian); Globigerina ciperoensis ciperoensis (Chattian); Globorotalia opima opima (Chattian); Globigerina ampliapertura (Rupelian); Cassigerinella chipolensis/ Pseudohastegrina micra (Rupelian). The Oligocene–Miocene (O/M) boundary is found to be conformable and is placed at the top of the Globorotalia kugleri Biozone. However, the Miocene/Pliocene (M/P) boundary is unconformable and is placed at the top of Praeorbulina glomerosa Biozone. Additionally, the established biozones have been regionally correlated with their equivalents in Tunisia and Egypt.