The Late Devonian (Frasnian/Famenian) mass extinction: a proposed test of the glaciation hypothesis

Abstract

It is argued in this paper that late Frasnian global cooling was the first step in the onset of the Late Palaeozoic Ice Age, and that the late Frasnian extinctions are analogous to the early Oligocene (Oi-1) extinctions that took place in the first step in the onset of the Cenozoic Ice Age. It is argued that the physical evidence for the existence of late Frasnian glaciation, like the Oi-1 glaciation, is largely geochemical: the sharp increases in δ 18 O values and positive δ 13 C anomalies that occurred in the late Frasnian and earliest Famennian. In addition to the geochemical evidence, also like the Oi-1 glaciation, stratigraphic calculations indicate a major sea-level fall occurred during the late Frasnian and early Famennian, a sea-level fall that is argued to have been glacially produced. It is here proposed that the best possible independent physical evidence for the existence of late Frasnian glaciation, other than the geochemical and sea-level evidence, would be the discovery of ice-rafted debris in marine sediments of late Frasnian age similar to the ice-rafted debris found in Oi-1 marine sediments (Zachos et al., 1992; Ehrmann and Mackensen, 1992).