Biostratigraphy and Ostracod Faunas of the Miocene Marada Formation of the Eastern Sirt Basin, Libya

Geology, Paleontology

Gammudi, Amar Mohamed

University:University of Glasgow

关键词: Geology, Paleontology;   

Others  :  http://theses.gla.ac.uk/78047/1/11007326.pdf

来源: University of Glasgow

【 摘 要 】

An attempt is made to define the biostratigraphy of the Marada Formation using the ostracod faunas for age determination and palaeoenvironmental analysis. The material studied is ditch cutting samples from the Miocene Marada formation of three wells drilled in the eastern Sirt Basin by the Wintershall company in concession 97, zone 2. The Marada Formation has previously been studied by several authors such as Desio, (1935) who dated as Early-Middle Miocene, with fewer studies on the ostracods, e. g. Innocenti and Pertusati (1984) and Szchechura (1989). 28 genera and 55 species of ostracods have been recorded; six species are new: Actinocythereis sirtensis sp. nov, Bythocypris tripoliensis sp. nov, Cyprideis maradaensis sp. nov, Cytheridea joshensis sp. nov, Hermanites zaltanensis sp. nov, Paijenborchellina keeni sp. nov; 22 species have previously been described; 9 can be closely compared with described species; and 18 left under open nomenclature. Many of the species previously described have a wide ranging distribution in the Miocene to Pliocene of the Mediterranean region and North Africa; some of these are restricted to the Lower Miocene, others to the Upper Miocene while no species diagnostic of the Middle Miocene have been found. Four ostracods biozones have been recognised in the Marada Formation: Biozone A is defined by the total range of Pokornyella deformis minor and indicates Lower Miocene (Aquitanian); Biozone B is defined as the interval between the last appearance stratigraphically of Pokornyella deformis minor and last appearance of Aurila soummamensis and is Lower Miocene (Burdigalian); Biozone C is an interval zone probably of Middle Miocene age, Biozone D is an assemblage zone indicating the base of the Upper Miocene. The Biozones were present in all three Wells. The Burdigalian biozone can be correlated with biozones of the Miocene in Turkey. The palaeoenvironments indicated by the ostracods are shallow marine (Infralittoral zone) with significant brackish levels (probably lagoonal) in the Burdigalian.