Structural context of the paleogeography of the Cenomanian-Turonian anoxic event in the eastern Atlas basins of the Maghreb

Abstract

The regional Cenomanian-Turonian (C/T) structural framework of surface and subsurface coupled with subsidence data inferred from palegeographic and organic-rich C/T isopachs map, generated in this work, from several basins, wells and outcrops of Tunisia and eastern Algeria was investigated and provide constraints on the structural and sedimentary evolution of this part of the southern Tethyan margin during the C/T times. La réduction des zones emergées depuis la Cénomanien déduit de la carte paléogéographique est mis en évidence.L'évolution globale est également amplifiée par les mouvements diapirique du Trias créant des rim-synclines subsidents, où les faciès riches en matière organique ont prévalu.

The Organic-Rich and Siliceous Bahloul Formation: Environmental Evolution Using Facies Analysis and Sr/Ca & Mn Chemostratigraphy, Bargou Area, Tunisia

“…The diapiric rise, starting from Aptian (and even before) to approximately middle Eocene was probably continuous, but it increased during periods of tectonic instability. Thus earlier diapiric movements and rise-up are super-imposed to the extensional features favouring depocenters individualisations in the central parts of rim-synclines (Soua et al, 2009). …”

“…Elsewhere, these syn-sedimentary features are represented by local slumping. Generally speaking, in north-central Tunisia as well as on the Pelagian Province, Cretaceous diapiric movements of Triassic salt played locally an important role in controlling C/T deposition, (Patriat et al, 2003;Soua and Tribovillard, 2007;Soua et al, 2009). They are characterized by a marked thickness reduction and partly by development of detrital deposition (sandstones, conglomerates).…”

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

“…(4) During the Albian, the geodynamic evolution is marked by the sealing of lower Cretaceous structures during an extensional phase that persisted to form graben systems promoting organicrich and siliceous strata deposition throughout upper Cenomanian to Lower Turonian times (Soua et al, 2009). The major faults in this area are represented by N140° and N70° trend features.…”

“…Mid-Cretaceous pelagic deposits outcropping in Northern Tunisia include organic-rich beds locally associated with high abundance of radiolarian microfauna, which are interpreted as the signature of the two global oceanic anoxic events OAE1 and OAE2 (Talbi, 1991;Saïdi & Belayouni;1994;Caron et al, 1999;Amédro et al, 2005, Heldt et al, 2008Khazri et al, 2009;Soua et al, 2009;Robascynski et al, 2010;Ben Fadhel et al, 2011). 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.…”

Planktonic foraminiferal turnover across the Cenomanian – Turonian boundary (OAE2) in the northeast of the Tethys realm, Kopet-Dagh Basin

“…Production of a lot of organic matter during the time of decreasing oceanic circulations leads to an anoxic condition and superimposition of three crises during the event: wide scale occurrence of black shales (Arthur & Premoli Silva 1982;Luciani & Cobianchi 1999;Coccioni & Luciani 2005), faunal turnovers (Leckie et al 1998;Keller et al 2001Keller et al , 2008Keller & Pardo 2004;Caron et al 2006;Soua et al 2009Soua et al , 2011) and a positive δ 13 C excursion (Paul et al 1999;). …”