Abstract: The Ordovician to Devonian succession in the in Murzuq Basin represents the most important part of the lower Paleozoic terrigenous Al Gargaf siliciclastic group, which consists of several formations such as the Ordovician Hawaz, Melaz Shuqran and Mamuniyat Formations and the Devonian Tadrart and Awainat Wanin Formations. Different integrated methods were used and implemented in order to understand lithology and sedimentary structures of the Ordovician, Silurian and Devonian formations. Firstly, intensive geological field trips were carried out and special attention was focused on Ordovician and Devonian reservoir sandstones and the Silurian source rocks. Secondly facies analysis and sequence stratigraphy methods were applied to figure out a simple sequence stratigraphic division of the Ordovician to Devonian succession based on outcrop sections, well logs and interpreted seismic sections. As a result of the petrographic field investigation and facies analysis based on seismic interpretation of the several seismic lines in the study area. Sequence boundaries of the Ordovician and Devonian succession on all seismic sections were identified by using specific reflection terminations such as onlap and erosional truncations features. 13 seismic facies were recognized, divided and classified for each of the examined stratigraphic formations (4 facies in Hawaz, 5 facies in Melaz Shuqran and Mamuniyat formations and 4 facies in the Tadrart and Awainat Wanin). A seismic facies classification chart was made on the basis of the classified seismic facies scheme, since depositional systems and types of seismic facies differ in each stratigraphic succession. Depositional sequences of sedimentary environments were identified from well logs and available 2D seismic sections and sequence stratigraphic frameworks were constructed for the Ordovician and Devonian formations. Based on the facies analysis and sequence stratigraphy interpretations, two different order sequences in the Ordovician to Devonian succession have been found and identified: The major sequences are possibly 2nd-order sequences in time duration. They are clearly traceable on all seismic sections. May be minor sequences are possibly 3rd-order sequences, and they are not traceable on all seismic sections clearly, but are recognized on well logs or outcrop sections. Eventually, all obtained information and that results were plotted on the different maps for each examined section to construct a depositional model and to estimate the maximum distributions of each formation separately on the basis of depositional system interpretations.

Keywords: Murzuq Basin, Al Gargaf siliciclastic group, Ordovician to Devonian succession, depositional system and seismic facies

Abstract: Eighty-five rock samples corresponding to the Palaeozoic formations were taken from two wells in the NC 200 Block of the Murzuq Basin. The study aimed to find out geochemical characteristics of Silurian Bir Tlacsin/Tanezzuft Formations, the Devonian Awaynat Wanin/BDS II Formations, and the Carboniferous Marar/Lower Marar Formations. Rock-Eval analysis, Total organic carbon (TOC) parameters and specific Gas Chromatography-Mass Spectrometry (GC-MS) biomarkers were applied to determine the potential hydrocarbon generation. Per se, Rocks are good sources and hold fair content of organic matter, crossing in the range of good accumulation, in which the very good source rocks have an organic carbon richness (TOC) reached of 3.7 wt%. The studied rocks are ranged from immature to late mature organic matter (OM) with total organic carbon richness (TOC) range between 0.4 – 3.7 wt%. Rock-Eval parameters S1, S2, S3, Tmax, S2/S3, OI, PI and HI of the source rock samples have values ranged from 0.02 – 0.3, 0.22 – 6, 0.36 – 4, 423 – 443, 24= 350, 0 – 0.27 and 42 – 384 respectively. The range of hydrogen index (HI) related to oxygen index (OI) displays that all kerogen types from Type II to Type III are exist and increase with depth. The Tmax parameter is wide-ranging among studied formations, indicating different levels of organic matter maturity, from immature oil window and to late mature for the Devonian-Carboniferous and Silurian source rocks, associated with more depth. Molecular composition analysis of n-alkanes and other biomarkers supported the findings of Rock-Eval pyrolysis data, revealing varied hydrocarbon signatures across the formations. The Carbon isotope analysis (δ13C) suggested multiple sources contributing to the generated oil, including Type I to Type III kerogens.

ABSTRACT: Study area situated in the center of the Hameimat trough which is located in the southeast of the Sirte basin. The Hameimat trough contains two of the largest oil fields in Libya, Gialo and Abu-Attifel fields. The Upper Cretaceous Rachmat, Tagrifet, and Sirte Formations are considered as the main source rock in Sirte Basin.Organic geochemical study of the Upper Cretaceous Rachmat, Tagrifet and Sirte Formations show these Formations have total organic carbon content values of 0.53% to 3.35% fair to excellent as source rock. The Kerogen types are type II and III mixed continental and marine organic matter. The thermal maturity of these formations indicates a mature stage in oil window.Oil saturation index (OSI: S1*100/TOC) shows that Sirte and Rachamt formations have low oil saturation, while the Tagrifet formation has good potential, where OSI exceeds 140 mg HC/g TOC in the most samples of the formation. The Tagrifet formation considers a good unconventional reservoir for shale oil, where the Sirte and Rachmat formations consider possible for shale oil with high risk.

Keywords: Unconventional reservoirs, Organic geochemistry, Sirte basin, shale oil and gas

Abstract: New footprints of theropod dinosaurs were discovered near Sebha city, southwestern Libya. It is the only known dinosaur record from the Jurassic to Lower Cretaceous period within the Messak Formation. The dinosaur footprints have been examined, counted, measured, photographed, and described to deduce the type of dinosaur, its size, shape, walking style, potential diet, and, if possible, its social interactions with other individuals. A total of 183 clear dinosaur footprints were found and documented, and at least two main sizes of footprints have been defined, characterized, and categorized into two groups: large footprints and small ones. The examined footprints made by an upright dinosaur stood and walked on its two hind feet on a humid layer composed of clay, silt, and fine sand. These footprints suggest they may belong to the theropod group of dinosaurs. The size of these footprints ranges from 20 to 60 cm, and the most common type is characterized by an angle of 50 to 70 degrees between the outermost digits. The foot size suggests that the trace makers' height at the pelvis ranged from 0.8 to 2.4 m, while the overall length of the creature reached 9 m from head to tail. A close examination of the footprints reveals almost equal distances between each footprint, indicating that the animals were moving with coordinated, normal steps and walking in their typical gait. Consequently, they were not in a state of chase or escape from any potential dangers. Based on the current state of knowledge, we believe there are two possible interpretations regarding the preservation of these footprints. Physical and chemical processes, such as consolidation, cementation, and the formation of a crust of iron oxides, played a crucial role in preserving the dinosaur footprints within fragile sediments primarily composed of silt and mudstone beds, which are covered by thin layers of sandstone.

Keywords: Murzuq Basin, Messak Formation, dinosaur footprints.

Abstract— Ninety-four rock samples were taken from the Middle to Late Devonian Awaynat Wanin, Early Carboniferous Marar, Late Carboniferous Assedjefar formations. The cuttings of Assedjefar Marar and Awaynat Wanin Formations collected from two wells, in the A1-163 oil field, locateed in the Murzuq Basin. RockEval Pyrolysis, Total Organic Carbon (TOC) and molecular biomarker (via the use of chromatographymass spectrometry, GC-MS) as geochemical parameters were applied to find out the types of kerogen, depositional conditions and level of organic matter maturity for representative samples. Such Formations are poor to excellent quantity of organic matter. Results of TOC related with remaining generation potential (S2) and hydrogen index (HI) data showed that the organic matter attributed to Type II/III and Type III kerogen (gas and oilprone organic matter), as well connected to S1 parameter indicated indigenous hydrocarbon exist. Ratios data of individual hydrocarbons, n-alkanes, isoprenoids and biomarkers parameters of Triterpanes and steranes indicate non-marine with marine organic matter deposited under non-marine conditions for Awaynat Wanin samples while Marar and Assedjiefar Formations deposited in nonmarine to deltaic conditions. The maturity data from Tmax, spore colour index and biomarker related parameters based on terpanes, steranes, and low molecular-weight hydrocarbons indicate the studied rocks are ranged from immature to mature.

Key Words— Awaynat Wanin Formation, Middle to Late Devonian, Kerogen, Biomarker, Rock Eval, Murzuq Basin