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

Abstract

Significant attention has been given, during the last decade, to Palaeozoic unconventional oil and gas shale in northern Africa where the productive Palaeozoic basins are located. New tentative strategies shed light on Mesozoic unconventional plays represented by Cretaceous shale reservoirs. In most petroleum systems the proven Cretaceous oceanic anoxic events (OAEs), represented mainly by the Fahdene and Bahloul Formations, played the main role in hydrocarbon generation with good distribution. Their deposition was restricted to the early Aptian (Bedoulian), the early/late Albian, and the Cenomanian-Turonian transition. Additional black shales have been detailed for the first time in Tunisia which relate to the Valanginian Weissert and late Hauterivian Faraoni events. Biostratigraphic and complete geochemical reviews have been undertaken from published papers and unpublished internal reports to better assess these important source intervals. These black shale levels, pertaining to OAEs, were deposited in almost deep marine environments during short-lived periods of anoxia (ca. 2 Ma). In the course of this review, thickness, distribution, and maturity maps have been established for each level using well data from published sources. ARTICLE HISTORY

Temporal and spatial changes of the submarine Cretaceous paleoslope in Northern Tunisia, inferred from slump folds analysis

“…This area exhibits also numerous outcropping salt structures belonging to the northeastern Maghreb salt province (Masrouhi et al, 2013;, (2) second, the Zaghouan-Ressas unit, acknowledged by last reviews to be the front of the Northern Tunisian Alpine Range. The present Zaghouan Thrust Fault corresponds to an inverted inherited fault, which during Mesozoic time, makes a paleogeographic line dividing a relatively shallow platform to the south, with a condensed Aptian section from a deep basin in the north (Morgan et al, 1998;Soua, 2016) with a thick Aptian-Albian section (Chihaoui et al, 2010).…”

Aptian–Albian shale oil unconventional system as registration of Cretaceous oceanic anoxic sub-events in the southern Tethys (Bir M’Cherga basin, Tunisia)

“…This sub-event identified in Tunisia for the first time by Talbi (1991) was manifested in the Center, the North and the North-East of Tunisia and covering a vast paleogeographic domain. OAE1a event is characterized by a diachronic and a clear variation of TOC richness and thickness confirmed by Soua (2016). This oceanic anoxic subevent is well documented and identified for the first time in the Italian Apennines as "Livello Selli" OAE1a (Coccioni and Galeotti 1994).…”

“…This Oceanic Anoxic Event occurred over a long period (113-109 Ma) with short-term paroxysms (≤ 1 Ma) that coincided with the accumulation and fossilization of significant amounts of organic matter in four black shale units during the four oceanic anoxic sub-events: OAE1a, OAE1b, OAE1c and OAE1d (Jenkyns et al 1990;Bralower et al 1994;Jarvis et al 2002;Leckie et al 2002;Soua 2016). The first marker (OAE1a) is of the Barremian-Aptian boundary identified by Schackoina cabri and Globigerinelloides blowi biozone (Weissert et al 1998;Sliter 1989;Bralower et al 1994) particularly in the south of France: the "Goguel livel" formation of Bréhéret (1994) and in Italy: the "Selli livel" formation of Coccioni and Galeotti (1994).…”

“…The Bir M'Cherga basin in the north-east of Tunisia is an exception and offers a unique opportunity to analyze and correlate them. Elsewhere, in the rest of the "Tunisian furrow" bordering the southern Tethyan domain, the main three sub-events (OAE1a, b, and d) had been identified and correlated with their counterparts of the global ocean (Soua 2016) while oceanic anoxic sub-event OAE1c, had never been reported in this area.…”

Cretaceous paleomargin tilted blocks geometry in northern Tunisia: stratigraphic consideration and fault kinematic analysis

“…Since or non-quantitative documentation on a large scale. Only few works attempt to solve the 561 geometrical reassembly by retracing long structural transects (Rouvier, 1977;Ben Ferjani et al, 1990; 562 Morgan et al, 1998, Khomsi et al, 2009, 2016) 563…”