The Hangenberg event is a bioevent that occurred at the end of the Famennian epoch (late Devonian) associated with the Late Devonian extinction (roughly 358.9 ± 0.4 million years ago); it was an anoxic event marked by a black shale. It has been proposed that this was related to a rapid sea-level fall due to the last phase of the Devonian Southern Hemisphere glaciation. It has also been suggested that it was linked to an increase in terrestrial plant cover, leading to increased nutrient supply in rivers. This may have led to eutrophication of semi-restricted epicontinental seas and could have stimulated algal blooms.