Ash Shabiyat Fm

The Ash Shabiyat Formation was defined by Havlicek and Massa (1973), and also known as “H9” Fm. (Fello et al., 2006). The Ash Shabiyat Formation can be easily examined close to the Ghat region (Fello, 2001).

References: Havlicek and Massa, 1973; Bellini and Massa, 1980; Pierobon, 1991; Fello, 2001; Fello et al., 2006; Alkhalas, 2006

The Ash Shabiyat Fm is 65m thick, and characterized by medium- to coarse-grained sandstone, with abundant Tigillites zones, and common trace fossils such as Cruziana and Harlania (Bellini and Massa, 1980). It can be divided into a lower and an upper unit. The lower unit comprises thin-bedded, flaggy sandstones, often ferruginous, containing Tigillites and Harlania. The thickness is about 25 m. Cross-bedding is rare, which is taken to indicate a deeper depositional environment. The upper unit, which reaches 40 m in thickness, is more thickly bedded and more extensively cross-bedded, and bears some similarity to the Hasawnah Formation (Hallett, 2002).

Trace fossils (Cruziana and Harlania), Graptolites (Normalograptus sp.)

From Google Gemini review of literature (Aug 2026): “Because the unit mostly consists of clean, barren quartz sandstones, its age is primarily determined by its stratigraphic position and microfossil correlation from surrounding layers. But it is broadly constrained to the Tremadocian to Floian stages of the Early Ordovician, and may extend into the Dapingian stage of the early Middle Ordovician. The Lower Boundary Estimate: Many regional stratigraphers place the base of the formation within the Tremadocian stage (the earliest stage of the Ordovician). It sits above the vast Cambrian-to-early-Ordovician Hasawnah Formation. The Upper Boundary Estimate: The formation shares a conformable, gradational boundary with the overlying Hawaz Formation. Well-documented palynomorphs (acritarchs and chitinozoans) date the lower-to-middle Hawaz Formation to the Darriwilian stage (Middle Ordovician). Consequently, the Ash Shabiyat Formation must span the time interval directly preceding it—the Floian and potentially the Dapingian stages.

Ash Shabiyat Formation is interpreted as a possible transition from a fluvial to a marine setting (Fello, 2001). The Ash Shabiyat Formation represents a marine transgressive unit in southern Libya (Alkhalas, 2006).