Stratigraphic Architecture and Depositional Environments of the Paleozoic Successions in Jabal Al-Hasawna and Wadi Ash-Shatti, SW Libya: A Field-Based Synthesis

Abstract

This paper presents a comprehensive field-based analysis of the stratigraphic successions and depositional environments in the Jabal Al-Hasawna and Wadi Ash-Shatti regions of southwestern Libya. Based on a detailed seven-day geological field excursion, the study documents a chronological sequence ranging from the Precambrian basement to Quaternary deposits, with a primary focus on the Paleozoic strata. Key formations investigated include the Al-Hasawna (Late Cambrian), Tanazzuft (Silurian), and the Devonian Awaynat Wanin Group (Bir Al-Qasr, Edri, Quttah, Dabdab, Tarut, and Ashkidah formations). The field data reveal a dynamic geological history characterized by significant transgressive-regressive cycles. The transition from the stable cratonic basement to the fluviodeltaic Al-Hasawna Formation is marked by a profound nonconformity. Subsequent Silurian marine transgressions deposited the graptolitic shales of the Tanazzuft Formation. The Devonian successions are notably characterized by coarsening-upward progradational cycles, intense bioturbation (dominated by Skolithos and Tigillites ichnofacies), and the widespread occurrence of ferruginous oolitic sandstones, indicating storm-dominated, shallow marine to restricted lagoonal environments. By integrating lithological, ichnological, and structural field observations across multiple sites, this study provides a unified model of the region's stratigraphic evolution, highlighting the complex interplay between sea-level fluctuations, sediment supply, and tectonic stability.