Note that the world 's richest deposits of fossils from the oligocene epoch are found in the badlands .
需要注意的是世界上渐新世年代最丰富的化石沉积物却是在坏地发现的。
Fossil plants from the eocene and oligocene epochs indicate that what 's now the qinghai-tibet plateau enjoyed a tropical-subtropical rainforest environment with growing areas of temperate flora in some mountainous areas .
They have also unearthed some clues from the ensuing oligocene , when the modern suborders of cetaceans-the mysticetes ( baleen whales ) and the odontocetes ( toothed whales ) - arose .
Since tha latest of cretaceous , the xiihu sag had been undergoing rifting stage during the paleocene and the eocene , inversion stagc during the oligocene and the miocene , and regional subsidence stage during the pliocene and the quaternary .
