<human>: Question: Oxygen from what kind of fossil were used to date the Hirnantian faunal stage?

Is The most-commonly accepted theory is that these events were triggered by the onset of an ice age, in the Hirnantian faunal stage that ended the long, stable greenhouse conditions typical of the Ordovician. a good answer to this question?

OPTIONS:
- yes
- no
<bot>: no