First direct age determination from the Jurassic radiolarian-bearing siliceous series (Jédidi Formation) of northwestern Tunisia

Abstract

International audienceOur study presents preliminary biostratigraphic results from the Jurassic siliceous series of northwestern Tunisia. For the first time, radiolarians are extracted from the Jédidi formation and provide a direct age determination. They are the first radiolarian fauna documented from Tunisia. Two age assignments are comprised within the following intervals: (1) Late Bathonian–Early Callovian, (2) Late Bathonian–Early Oxfordian. These ages are compatible with recent stratigraphic synthesis proposed for the Jurassic series of Tunisia. The data suggest the correlation of the Jédidi formation with siliceous series of Middle–Late Jurassic age from the external zone of the Maghrebides belt rather than with true oceanic units from the Maghrebian flyschs or the internal zones of western Tethys

Jurassic radiolarian-bearing series of Tunisia: biostratigraphy and significance to western Tethys correlations

“…It is worth noting that through all studied successions, the siliceous facies vary along sections. Contrary to previous interpretations, Cordey et al (2005) established that these successions are actually not "true" radiolarites s.s., as radiolarian-rich layers alternate with carbonates which are locally silicified. Carbonate proportions within siliceous limestone beds increase towards the top of the formation, grading into marl-limestone alternations of the Béni Kleb Fm.…”

“…bernès et al 1996) and late Bajocian-late Oxfordian in more recent syntheses (Soussi et al 1998;Soussi 2002Soussi , 2003]. Cordey et al (2005) recently established the first preliminary direct age determination of the Jédidi Fm, questioning the previous sedimentological interpretations that these series were true radiolarites. We present here more complete results obtained at the type locality of the Jédidi Fm and other sections from the area (J. Chaâbane, Oued (O.)…”

Integrated biostratigraphy and regional correlations of Upper Jurassic–lowermost Cretaceous series in northern Tunisia

“…Considering that the OxfordianKimmeridgian boundary is now placed below the Planula Zone, the highest beds of the section were dated as lowermost Kimmeridgian (Idoceras planula Zone). We presented a first preliminary direct age determination of the partly coeval Jédidi Fm (TT) using radiolarians (Cordey et al 2005) where we also questioned previous interpretations that these series are "true" radiolarites. Then, we obtained more complete results at the type locality of the Jédidi Formation, J. Chaabane and Oued (O.)…”

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

“…Several studies have stated the close association between organic-rich sediments and radiolarian in the Atlantic and Tethyan realms (Marcucci-Passerini et al, 1991;O'Dogherty, 1994;Erbacher & Thurow, 1998;Danelian et al, 2004Danelian et al, , 2007. In North African margins, the radiolarian biostratigraphy have focused upon radiolarianbearing Jedidi Formation which has been thoroughly discussed by Cordey et al, (2005) and Boughdiri et al, (2007). The first attempts at dating radiolarian series in Northern Tunisia show that radiolarian associated with carbonate-siliceous beds, have yielded useful diagnostic radiolarian assemblages (Cordey et al, 2005;Soua et al, 2006;Ben Fadhel et al, 2010).…”

“…In North African margins, the radiolarian biostratigraphy have focused upon radiolarianbearing Jedidi Formation which has been thoroughly discussed by Cordey et al, (2005) and Boughdiri et al, (2007). The first attempts at dating radiolarian series in Northern Tunisia show that radiolarian associated with carbonate-siliceous beds, have yielded useful diagnostic radiolarian assemblages (Cordey et al, 2005;Soua et al, 2006;Ben Fadhel et al, 2010). Albian and Cenomanian-Turonian black shales of Northern Tunisia were considered to have good generative oil source rock (Layeb, 1990;Saidi & Belayouni, 1994;Bechtel et al, 1998;Ben Fadhel et al, 2011).…”