agc 11/11/94, 11/28/94 broke it up into pages

bmw 11/11/94, 11/28/94 added new text

brs 5/20/98 updated content, added Tectonics page

Paleozoic pages updated to reflect Geological Society of America (GSA) 1999 Geologic Timescale, compiled by A.R. Palmer and J. Geissman
-- S. Rieboldt, Nov. 2002