Graptolite biostratigraphy of the E1-NC174 core, Rhuddanian (lower Llandovery, Silurian), Murzuq Basin (Libya)

 

Authors: Loydell D

Published in: Bulletin of Geosciences, volume 87, issue 4; pages: 651 - 660; Received 19 August 2011; Accepted in revised form 3 January 2012; Online 17 April 2012

Keywords: Silurian, Libya, graptolite, Llandovery, Rhuddanian, hot shale, North Africa, Tanezzuft,

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Abstract

The graptolite biostratigraphy of the Rhuddanian (lower Llandovery, Silurian) of the E1-NC174 core, Murzuq Basin, Libya is described. The generally low diversity graptolite assemblages include both North African endemic taxa and cosmopolitan species. The lower part of the cored interval, below the ‘hot’ shale, is dominated by Normalograptus tilokensis, a species previously considered to be confined to the Upper Ordovician, but which almost certainly ranges into (or perhaps occurs only in) the lower Silurian. As in the BG-14 core, Jordan, the base of the ‘hot’ shale lies just above the first appearances of Neodiplograptus africanus and Normalograptus rectangularis. The latter species dominates throughout the mid Rhuddanian ‘hot’ shale interval, with the highest strata in the core, of late Rhuddanian age, yielding abundant Neodiplograptus fezzanensis.