Causes for Triassic-Jurassic mass extinction

The Triassic-Jurassic mass extinction is the event owns most of the debates for the causes to it. Several theories for explaining this mass extinction have been suggested, but none of them have answered why it happened.

Generally, evidences have shown there were gradual climate changes, a pulse of oceanic acidification or sea-level fluctuations at that time. They can be causes of mass extinction but according to the TJME situation, those causes cannot explain why event happened so suddenly [1].

Another possible cause-asteroid impact also seems not enough for causing such a sudden big mass extinction as the carbon record presents that there were no big asteroid impacts at that period of time [2].

Then, massive volcanic eruptions, which would emit carbon dioxide or sulfur dioxide and aerosols, could cause global warming or cooling also can be the reason for the event [3]. The exist evidence proofs that there was an increase in  carbon dioxide in the atmosphere at that boundary.

Except the debating of the causes, there are also some one argued for that TJME was not the product of a single major event [4]. They preferred to not treat the event as a mass extinction event but a simply prolonged turnover of species across a considerable amount of time.

Reference:

1. T.M.Quan, et al. (2008) Nitrogen isotope and trace metal analyses from the Mingolsheim core: Evidence for redox variations across the Triassic-Jurassic boundary", Global Biogeochemical Cycles

2. S.Roff. (2011) Dark days of the Triassic: Lost world

3. J.F.Hubert et al. (2001) Stability of atmospheric CO₂ levels across the Triassic/Jurassic boundary

4. http://www.britannica.com/EBchecked/topic/1523109/end-Triassic-extinction