The Albian oceanic anoxic events record in central and northern Tunisia: Geochemical data and paleotectonic controls

Abstract

The Albian organic-rich successions of the lower part of the Fahdene Formation (Albian to Cenomanian, Tunisia) were studied using sedimentology (analysis of carbonate contents and observation of thin sections), bulk organic geochemistry (Rock-Eval pyrolysis), and molecular biomarker distributions. The selected outcrops cover different structural domains from western central Tunisia (Jebel Hamra) to the Diapir zone or the Tunisian Trough (Koudiat Berkouchia, Jebel Ghazouan and Ain Asker from the southwest to the northeast, respectively). Total Organic Carbon values between 0.17 and 3.43% evidenced the record of the Albian oceanic anoxic events OAE1b and OAE1c in this southern Tethys margin. Rock-Eval data and molecular biomarkers (n-alkanes, steranes and terpanes) revealed thermally mature organic matter (OM) consisting of a mixed Type II/III OM (marine planktonic and continental origins). The abundant tricyclic terpanes, C30 17α(H) Diahopanes, and the regular decrease of homohopanes (C31 to C35) in the terpane series, were also indicative of a high contribution of bacterial OM that had been developed under stagnant dysoxic/anoxic environments.

Sequence stratigraphy and organic geochemistry: An integrated approach to understand the anoxic events and paleoenvironmental evolution of the Ceará basin, Brazilian Equatorial margin

“…Globally, this warming is explained by high atmospheric CO 2 concentrations triggered by volcanic activity through periods of seafloor spreading (Arthur et al, 1985;Bice et al, 2006;Hofmann et al, 2008;Turgeon and Creaser, 2008). This hydrothermal volcanic influence may have played a role in oceanic water circulation (Hays and Pitman, 1973;Paytan et al, 2004), causing the warming of bottom waters of low circulation rates and less dissolved oxygen (Khalifa et al, 2018).…”

Depositional Conditions and Nature of Source Rocks of the Upper Part of the Balambo Formation in Northeastern Iraq Based on Rare Earth Elements Data

“…Very warm climatic conditions characterize the Cretaceous period, especially the Albian, the minor temperature gradient between the equator and the poles, lack of ice, rise in sea level, and abundance of volcanic and tectonic activities [1,2]. The Balambo Formation is one of the widely spread Cretaceous sequences in northeastern Iraq and represents the bathyal facies deposited in a basin extending northwest-southeast in the northeastern part of Iraq [3].…”

Organic geochemical, palynofacies, and petrographic analyses examining the hydrocarbon potential of the Kharita Formation (Albian) in the Matruh Basin, northwestern Egypt

“…Lower Cretaceous Albian strata in the northern and southern Mediterranean regions contain intraformational organic-rich deposits which show significant hydrocarbon source rock potential, such as in SE France (Herrle et al, 2003;Bornemann et al, 2005), Italy (Katz et al, 2000), and Tunisia (e.g., Ben Fadhel et al, 2011;Khalifa et al, 2018). However, information on the organic richness and petrography, and hence the hydrocarbon source rock potential of the Albian deposits of the southeastern Mediterranean area, specifically of Egypt, is still fragmentary.…”