Geochemical characterization of Upper Cretaceous organic-rich deposits: Insights from the Azraq Basin in Jordan

• Published in: Journal of Asian earth sciences Vol. 276; p. 106365
• Main Authors: Fathy, Douaa, Farouk, Sherif, Qteishat, Abdelrahman, Ahmad, Fayez, Sami, Mabrouk, Al-Kahtany, Khaled, Lee, Eun Young
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2024
• Subjects: Biomarker; Isotopes; Maturity; Oceanic Anoxic Event; Upper Cretaceous; Upwelling; Upwelling; Oceanic Anoxic Event; Biomarker; Upper Cretaceous; Isotopes; Maturity
• ISSN: 1367-9120
• DOI: 10.1016/j.jseaes.2024.106365

•Maastrichtian and Turonian deposits stand out as superior hydrocarbon source rocks.•Increased thermal maturity observed in pre-Maastrichtian sediments.•Upper Cretaceous deposits indicate a marine origin and prevalent anoxic conditions.•Organic richness in Maastrichtian/Turonian deposits is tied to upwelling and OAE2. Cretaceous sedimentary successions in Jordan are among the most promising unconventional global petroleum resources. The Upper Cretaceous deposits in the Azraq Basin in Jordan were analyzed using Rock-Eval pyrolysis, stable carbon isotopes, vitrinite reflectance, and biomarkers, as well as 1D basin modeling. This study aims to evaluate source input, depositional environment, burial history and potential for hydrocarbon generation of the Upper Cretaceous organic-rich deposits in Jordan. The Upper Cretaceous samples exhibit variable source rock potential. Maastrichtian samples are very good, primarily oil-prone, while Campanian and Cenomanian samples range from fair to poor, with Turonian samples showing good petroleum generation potential. Thermal maturity analysis of Cretaceous samples reveals higher maturity in Turonian and Cenomanian samples compared to the thermally immature Maastrichtian and Campanian samples based on the maximum temperature of pyrolytic hydrocarbons generation, vitrinite reflectance, production index and biomarker indicators. The molecular fossils data suggest that the organic matter of these source rocks was primarily of marine phytoplankton origin, with considerable contributions from microbial biomass, and deposited under oxygen-depleted bottom water conditions. Additionally, the resemblance in molecular composition between Cretaceous source rocks and crude oil samples suggests a common origin for the hydrocarbons. The highest contents of organic matter have been recorded at the top of the Maastrichtian and at the bottom of the Turonian sections. These findings correspond with Maastrichtian upwelling deposits in North Africa and the Middle East, as well as with deposits from the Cenomanian-Turonian Oceanic Anoxic Event (OAE2).