The Paleocene-Lower Eocene series of the Gafsa basin (South-Central Tunisia): integrated stratigraphy and paleoenvironments

In the Gafsa basin, the Paleocene-Eocene interval is represented by the evaporite deposits of Thelja Formation, the phosphatic series of Chouabine Formation, and the carbonate bed of Kef Eddour Formation. The Thanetian-Ypresian transition lies within the lower unit (C1) of the Chouabine Formation. These different facies characterize circalittoral to margino-littoral paleoenvironments. Sedimentological analyzes of this interval allowed to define eleven genetic sequences. The comparison of these sequences with the global chart of Sneeden and Liu ( 2010 ) shows a good correlation with the third-order cycles. In the eastern part of the Gafsa basin (Jebel Chemsi), the Paleocene-Ypresian transition is characterized by a marly-carbonate series deposited in an isolated open marine environment not recording minor relative sea-level changes. The Selandian Pg10 major maximum flooding is detected within the S2 sequence of the Oued Thelja section. The Thanetian-Ypresian transition (55.8 Ma), identified in the S7 sequence of this section, coincides with a major sea-level rise at the origin of phosphate sedimentation onset in the Gafsa basin and around the Kasserine Island.