Geology. By esthergorham Period: Jan 1, 1909 to Jan 1, 2009 Historical Geology Jan 1, 1921 Cambrian 570m-500m Jan 1, 1932 ordovician 500m-435m Jan 1, 1939 Sulurian 435m-395m Jan 1, 1948 Devonian 395m-345m Jan 1, 1959 carboniferus 345m-280m Jan 1, 1969 permain 280m-225m Jan 1, 1974 triassic 225m-195m Jan 1, 1984 jurassic 195m-136m Jan 1, 1997 cretaceous 136m-65m Sep 30, 2008 tertiary 65m-1.8m Jan 1, 2011 quaternary 1.8m-present
