PALYNOMORPH IDENTIFICATION AND PRELIMINARY PALYNOSTRATIGRAPHY OF THE SILURIAN TANNEZUFT AND AKAKUS FORMATIONS IN THE LIBYAN GHADAMES BASIN

The Ghadames Basin in northwest Libya has generated a plentiful amount of oil and gas, sourced primarily from the lower Silurian anoxic black shales (aka “hot shales”) at the base of the Tannezuft Formation. These shales are dark grey in color, fissile, and contain substantial amounts of organic matter as well as radioactive minerals. The Silurian System in the Ghadames Basin consists of both the Tannezuft and the overlying Akakus formations. For this study, coarse (250–300 µm) sieves were used during sample processing to avoid breaking large chitinozoan specimens. To date, 15 samples from three wells that collectively cover the entire Silurian in the northeastern Ghadames Basin have been studied. These samples yielded a diverse group of marine and non-marine palynomorphs, including acritarchs, chitinozoans, scolecodonts, prasinophytes, embryophytic spores, and cryptospores. Identified species include the chitinozoans Ancyrochitina ancyrea and Sphaerochitina concava, the acritarchs Diexallophasis denticulata, Cymbosphaeridium pilar, and Leiosphaeridia sp., and the spores Archaeozonotriletes chulus, and Ambitisporites avitus. These species (and others) allowed for robust age determination and enhanced stratigraphic correlation between the three wells. The generated data provide improved age constraints on the history of sedimentary organic matter accumulation and preservation in the most important source-rock horizons in the Ghadames Basin.