ABSTRACT FOR TALK:

Chitinozoans and early Silurian ‘hot’ shales − a case study from North Africa and the Middle East

Anthony Butcher

School of Earth & Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth, PO1 3QL, UK.

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Early Silurian ‘hot’ shales, characterized by high gamma-ray readings from authigenic uranium, are important hydrocarbon source rocks in North Africa and the Middle East, with TOC values of up to 17% (Lüning et al. 2000).

Recent studies have highlighted the essential role of high-resolution biostratigraphy in identifying and dating such ‘hot’ shales (e.g. Loydell 2007), and have demonstrated that there are in fact several such ‘hot’ shales in the lower Silurian, rather than a single ‘basal  organic-rich (‘hot’) shale unit’ (Lüning et al. 2000).  Combined with carbon isotope and acritarch morphological data, studies on the BG-14 core of southern Jordan have shown that the ‘hot’ shale within it was deposited during a minor marine regression (Loydell et al. 2009), as opposed to the transgressive model of deposition proposed by previous authors.

Chitinozoan data from the E1-NC174 core of south-western Libya have dated the ‘hot’ shale as the same middle Rhuddanian age as that of the BG-14 core.  The ‘hot’ shale intervals within each core also display a marked decrease in chitinozoan abundance, while TOC values increase overall.  Such similarities between the two ‘hot’ shales suggest that they were deposited under similar environmental conditions.

References

Loydell, D. K. (2007).  Graptolites from the Upper Ordovician and lower Silurian of Jordan.  Special Papers in Palaeontology, 78, 1−66.

Loydell, D. K., Butcher, A., Frýda, J., Lüning, S. and Fowler, M.  (2009).  Lower Silurian ‘hot shales’ in Jordan: a new depositional model.  Journal of Petroleum Geology, 32, 261−270.

Lüning, S., Craig, J., Loydell, D. K., Štorch, P. and Fitches, B. (2000). Lower Silurian ‘hot shales’ in North Africa and Arabia: regional distribution and depositional model.  Earth-Science Reviews, 49, 121−200.