Ichnology of Lower Cretaceous prodelta and delta front deposits of the Sidi Khalif Formation, Central Tunisia

This paper describes the ichnology and sedimentology of the middle Berriasian sedimentary succession of the Sidi Khalif Formation outcropping in Jebel Meloussi, Central Tunisia. The succession records deltaic progradation above outer shelf deposits and shows the vertical stacking of thickening and coarsening-upward parasequences dominated by hummocky cross-stratification, parallel lamination and abundant gutter casts. The mudstones and the thinly bedded fine-grained sandstones of the prodelta are characterized by scarce and low diverse horizontal trace fossils of the impoverished distal Cruziana ichnofacies, including cf. Thalassinoides , Phycosiphon , Planolites , Helminthoidichnites and cf. Helminthoidichnites . In contrast, trace fossils of the wave-dominated delta-front are dominated by deposit-feeding ichnotaxa, such as Rhizocorallium commune , Arenicolites isp., R. ? jenense , Thalassinoides and Planolites , which represent the proximal Cruziana ichnofacies. The lack of bioturbation structures in the amalgamated hummocky cross-stratification beds of the delta front is mostly related to the high frequency and/or high intensity episodic erosional amalgamation and deposition associated with storms. The difference between Rhizocorallium ichnospecies help to depict the erosional discontinuities bounding parasequences. The transgressive surfaces (TS) are characterized by R. ? jenense and by R. commune.