LATE DEVONIAN BIOEVENTS: WHAT MUST BE CONSIDERED?

During the Late Devonian two major events affected the marine fauna – the Kellwasser (KW) Event near the Frasnian/Famennian (mid-Late Devonian) stage boundary and the Hangenberg Event close to the Devonian/Carboniferous boundary. Both can be traced globally and the debate on their nature – especially their cause(s) – is vivid, long-lasting, and on-going. Although clearly focused on the KW Event, a number of arguments arising from the enormous amount of research during previous decades can be used to infer to general aspects of event-related patterns.

Among the questions that must be considered are those of what may have been causing globally distributed events in the Late Devonian, what was the “normal” situation present when the “unusual” cause(s) affected the biota, which groups of organisms were most affected, were events selective, and did a given event have negative or positive effects on evolutionary rates? Some of the results taken from a vast number of studies have to be evaluated, including theorized extraterrestrial impacts, climatic deterioration, plate tectonic reorganization, and oceanographic changes. Further, of prime interest are questions regarding ‘extraterrestrial’ vs. ‘Earth-bound’ mechanisms and ‘single’ vs. ‘multi-causal’ events.