Abstract

A comparison of benthic foraminifers from lower Albian black shales at Ocean Drilling Program Site 1049 with modern and Mesozoic high carbon flux/low oxygen assemblages indicate that no preferential test shape characterizes benthic foraminifers from dysaerobic environments, as almost the entire spectrum of test morphologies is represented within these assemblages. The lower Albian benthic foraminiferal assemblages from Site 1049 are the first black shale assemblages to be dominated by Fursenkoina viscida, Ellipsoidella cuneata, Pleurostomella reussi and Osangularia schloenbachi, all members of the suborder Rotaliina. Thus, early Albian black shale assemblages differ markedly from Aptian and Jurassic assemblages dominated mainly by representatives of the suborders Textulariina and Lagenina. Members of the suborder Rotaliina continued to radiate profusely during the Late Cretaceous and Cenozoic, eventually giving rise to a large proportion of the modern fauna, including many of the high productivity/low oxygen taxa. There is no evidence for a progressive morphological adaptation to low oxygen with time.

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