Radiolarian Age Constraints of Mid-Cretaceous Black Shales in Northern Tunisia

Cretaceous oceanic anoxic events (OAEs) recorded in the northern margin of Africa as possible oil and gas shale potential in Tunisia: An overview

“…Their main distribution occurred in: (1) the Carnian, (2) the Toarcian, (3) the Callovian, (4) the late Hauterivian, (5) the Bedoulian, (6) the Albian, (7) the Cenomanian-Turonian transition, and (8) with reduced importance in the Coniacian-Santonian transition (Soussi et al 1992(Soussi et al , 1998M'Rabet et al 1995;Arfaoui and Montacer 2004;Soua and Tribovillard 2007;Elkhazri et al 2009;Soua et al 2011b;Ben Fadhel et al 2012;Ouadday and Saddem 2012;Soua 2013a;Soua and Chihi 2014;Soua 2014b).…”

“…In the Nebeur area, several authors (e.g. Salaj 1981;Saidi 1993;Tandia 2001;Ben Fadhel et al 2012) mentioned the detrital input within early Albian strata of the northern Tunisian basins, which accumulated marls and shaly limestones and black shales (Souquet et al 1997) within tilted blocks and the Triassic salt tectonics regime. This configuration results in strong lateral thickness and facies variations of the Albian strata ( Figure 18; see Figure 17a for the location).…”

“…Generally, it consists of green shales interbedded with bioclastic limestones partly dolomitized followed by a conglomeratic bed, which is in turn overlain by a thick shale package with thin limestone intercalations displaying pelecypods, crinoids, belemnites, Ticinella raynaudi, and Ticinella primula (Rami 1998;Chihaoui 2008;Ben Fadhel et al 2012). The Allam (source rock, middle Albian) is composed of alternating dark grey-to black-coloured marls and decimetric beds of laminated limestones, which consist of mudstones and wackestones.…”

“…The overlying series are composed of laminated limestone, which consists of mudstone and wackestone beds, including decimetric organic-rich shale-marl interbeds. The basal shales consist of Rotalipora subticinensis (Rami 1998;Ben Fadhel et al 2012 Hedbergella planispira member (latest Albian), consists of relatively thick dark shales and marls admitting several argillaceous limestone beds. This unit is overlain by organic rich shales and marls containing ammonites and abundant planktic foraminifera indicating the latest Albian (Ticinella subticinensis).…”

“…The second sequence starts with a basal conglomeratic level (D9). In general, the lowermost part of the Allam member may still belong to either the lowstand systems tract (LST), such as in the Nebeur area (Ben Fadhel et al 2012), or the shelf margin wedge (SMW), such as in a proximal setting in the Tajerouine area (Chihaoui 2008), where Burollet (1956) first described the lower part of this member as consisting of calcispheres and echinoderm debris, belemnites, and fragments of ammonites, originating probably from the higher shelf (Supplementary Figure 3).…”