Browsing by Author "Rasul, Syed"

Latest Ordovician-earliest Silurian Tanezzuft Formation shales recovered from core material of the shallow bore-hole JA-2 drilled in Jebel Asba at the eastern margin of the Kufra Basin, southeastern Libya, yielded well-diversified palynomorph assemblages with transparent and brownish to yellowish vesicles and organic matter (visual kerogen Types 1 and 2) from depth interval 4620 to 67.82 m. In addition, miospores including cryptospores, and Tasmanites sp. ("Tasmanites with nodules"), scolecodonts, and a stratigraphically significant palaeo-marker, the enigmatic, tubular organic structure Tortotubus protuberans, were also recorded frequently in most samples. Kerogen colour based on miospores (TAI <3) and chitinozoan reflectance indicate an immature facies for oil generation. The two uppermost samples (from 3333 m and 46.20 m depths) and the lowermost ones (from 67.92 to 7321 m depth) contain rare palynomorphs and other organic remains and have been partially affected by oxidation. Furthermore, palynological and palynofacies analyses were carried out on cuttings from an old well (UN-REMSA well), ca. 530 m towards the NNE from well JA-2. The composition of the organic residue is similar in both wells. However, the UN-REMSA well yields fairly numerous chitinozoans, scolecodonts and biofilms but lacks the "thread-like structures" and "Tasmanites with nodules" observed in well JA-2. All the investigated samples in well JA-2 are dominated by a single chitinozoan species, Euconochitina moussegoudaensis Paris (in Le Herisse et al., 2013). Based on correlation with chitinozoan-bearing strata around the Ordovician-Silurian boundary, the analysed samples from well JA-2 and from the UN-REMSA well are regarded as post-glacial, but still of either latest Hirnantian age, or at least no younger than earliest Rhuddanian. A well-diversified acritarch, miospore and cryptospore assemblage recorded in well JA-2 supports a marginal marine (nearshore) depositional environment This assemblage is no older than earliest Rhuddanian yet the latest Hirnantian age of the assemblage cannot be completely ruled out as our current knowledge on the post-glacial, latest Hirnantian acritarch and miospore assemblages is poorly documented in North Africa. (C) 2013 Elsevier B.V. All rights reserved.

This work presents palynological and palynofacies analyses from early Silurian Tanezzuft Formation shales recovered from core material of borehole CDEG-2a drilled in Dor el Gussa at the eastern margin of the Murzuq Basin, southern Libya. The material has yielded well-diversified palynomorph and chitinozoan assemblages and organic matter from a depth interval of 37.41 to 50.64 m. The interval above 37.41 m is weathered and barren of palynomorphs. The palynomorph assemblage present from the 37.41-50.64 m interval is early Llandovery (Rhuddanian-early Aeronian) in age and was deposited in a shallow, open marine (but proximal) environment with a minor landward shift between 43.02 and 46.13 m. The oldest chitinozoan assemblage recorded in the studied core samples can be referred to the fragilis regional Biozone. However, because the relative abundance of Spinachitina fragilis is low, it is considered here that the deepest part of the borehole (at 50.64 m) does not penetrate the actual base of the Rhuddanian. Thus, a Rhuddanian-earliest Aeronian age is retained here for the corresponding strata in borehole CDEG-2a. The core includes the boundary between the fragilis and nuayyimensis biozones, which was until now unknown from southern Libya. Furthermore, we describe a new chitinozoan species, Angochitina murzukensis sp. nov. The intervals 37.41-42.36 m and 46.48-50.64 m show a dominance of amorphous organic matter (AOM) Types 1 and 2, suggesting an oil-prone potential, in contrast to interval 43.02-46.13 m, which is dominated by land-derived (vitrinite) Type 3 suggesting a gas-prone potential. The Ordovician-Silurian boundary and therefore the glacial-related Late Ordovician deposits have not been penetrated by the borehole. In all likelihood, this boundary is not far below the bottom of borehole CDEG-2a. (C) 2012 Elsevier B.V. All rights reserved.