Biostratigraphy of a Silurian ‘hot’ shale from western Iraq

Graptolites from the upper ‘hot’ shale from the Akkas-1 well, western Iraq demonstrate that it is of early Wenlock Monograptus riccartonensis Zone age, somewhat younger than the Llandovery age previously ascribed to it. Chitinozoans from the same sample are poorly preserved and can be identified only tentatively. The riccartonensis Zone was characterized globally by lowered sea-levels during an interval (Sheinwoodian) of otherwise high eustatic sea-level. Increased TOC levels have been recognised at this stratigraphical level also at localities on the palaeocontinents Avalonia and Baltica.