Late Devonian extinction is one of the five major mass extinction in earth history. It happened in 440 Ma years ago. It is also called the Frasnian Famennian Mass extinction. The Devonian is familiar with the diverse range of fishes and it is called the age of Fish. The Late Devonian extinction died out more than 70-80% of all species and 20% of all families during that time. The duration of the extinction was 20-25 Ma (Million Years) according to the famous geologist Thomas Algeo et. al. (2000).
The Late Devonian extinction event consists of two separate events;
- Kellwasser Events at the Frasnian Famennian Boundary
- Hangeberg Events at or near the Devonian and Carboniferous Boundary.
The organism extinct were mainly, ammonites, benthic foraminifera, jawless fishes, trilobites, brachiopods etc.
The main Causes of the Late Devonian extinction:
There are many causes has been proposed so far for the Late Devonian Mass Extinction, like, Asteroid impact, Plate tectonics, Sea level changes, Climate change, Global anoxia (Oxygen-poor bottom water), etc. One of the most accepted hypotheses for the extinction is a flourish of terrestrial vegetation. This hypothesis is proposed by Thomas Algeo. According to this idea, the highly emerging terrestrial vegetation developed and cause the high input of the nutrients in the sea water. The excess amount of nutrient (Ca, Mg) remove the CO2 from the atmosphere. The loss of this greenhouse gas cools the atmosphere with sea level drop and causes the mass extinction. Another group of scientist claimed that this terrestrial plant cause soil erosion and high input of nutrition cause the high primary production which causes anoxic bottom water and died out organisms and small creatures.
So, about the Late Devonian extinction still, scientist need to explore the scenario of the cause of the mass extinction.