First record of palynomorph assemblages from the Arshad Sandstone (Late Cretaceous), Sirte Basin, north-central Libya

Abstract

This paper presents the first record of identifiable palynomorph assemblages from the Arshad Sandstone, Sirte Basin, north-central Libya. Ninety core samples from five different wells were macerated to isolate palynomorphs, but 78 samples turned out to be barren. Among the 12 productive samples, the preservation of palynomorphs was generally poor to fair, limiting identifications at species level. However, despite these limitations workable assemblages were recovered from a few productive samples. Since palynomorph preservation is poor, many forms could only be identified at the generic level and some were unidentifiable. A few stratigraphically significant dinoflagellate cysts were identified at the species level. Palynomorph diversity is fairly high including both terrestrial (angiosperm and gymnosperm pollen grains, spores, algal and fungal remains) and marine (dinoflagellate cysts, acritarchs and foraminiferal remains) forms. The lithology of the Arshad Sandstone is quite diverse; variables include very hard and silicified sandstones, massive shales, sandy dolomites, and dolomitic sandstones. Characteristically all these sediments are massive, very hard, and occasionally bioturbated. No identifiable or datable macro- or mega-fossils are known from this stratigraphic unit, and previous attempts to isolate palynomorphs have been unsuccessful. The present palynological study indicates that these sediments were deposited in diverse environments ranging from nearshore terrestrial to shallow marine (inner shelf). Dinoflagellate cyst species indicate that the Arshad Sandstone is of Campanian–Maastrichtian age.