ERA                PERIOD             EPOCH                         CODE

1 Cenozoic         0                  0                             100
                   1 Quaternary       0                             110
                                      1 Recent                      111
                                      2 Pleistocene                 112
                                      9 Pliocene-Pleistocene        119
                   2 Tertiary         0                             120
                                      1 Pliocene                    121
                                      2 Miocene                     122
                                      3 Oligocene                   123
                                      4 Eocene                      124
                                      5 Paleocene                   125
                                      9 Cretaceous-Tertiary         129
                   3 Mesozoic-Cenozoic                              199

2 Mesozoic         0                                                200
                   1 Cretaceous       0                             210
                                      1 Upper                       211
                                      4 Middle                      214
                                      7 Lower                       217
                                      9 Jurassic-Cretaceous         219
                   2 Jurassic         0                             220
                                      1 Upper                       221
                                      4 Middle                      224
                                      7 Lower                       227
                                      9 Triassic-Jurassic           229
                   3 Triassic         0                             230
                                      1 Upper                       231
                                      4 Middle                      234
                                      7 Lower                       237
                                      9 Permian-Triassic            239
                Paleozoic-Mesozoic                                  299

3 Paleozoic       0                   0                             300
                Upper Paleozoic                                     301
                  1 Permian           0                             310
                                      1 Upper                       311
                                      4 Middle                      314
                                      7 Lower                       317
                                      9 Pennsylvan.-Permian         319
                  2 Pennsylvanian     0                             320
                                      1 Upper                       321
                                      4 Middle                      324
                                      7 Lower                       327
                                      9 Carboniferous               329
                  3 Mississippian     0                             330
                                      1 Upper                       331
                                      4 Middle                      334
                                      7 Lower                       337
                                      9 Devonian-Mississipp.        339
                  4 Devonian          0                             340
                                      1 Upper                       341
                                      4 Middle                      344
                                      7 Lower                       347
                                      9 Silurian-Devonian           349
                  5 Silurian          0                             350
                                      1 Upper                       351
                                      4 Middle                      354
                                      7 Lower                       357
                                      9 Ordovician-Silurian         359
                  6 Ordovician        0                             360
                                      1 Upper                       361
                                      4 Middle                      364
                                      7 Lower                       367
                                      9 Cambrian-Ordovician         369
                  7 Cambrian          0                             370
                                      1 Upper                       371
                                      4 Middle                      374
                                      7 Lower                       377
                                      9 Proterozoic-Cambrian        379
             Proterozoic-Paleoz.                                    399

4 Proterozoic     0                   0                             400
                  1 Upper             0                             410
                  2 Hadrynian         0                             420
                  4 Middle            0                             440
                  5 Helikian          0                             450
                  7 Lower             0                             470
                  8 Aphebian          0                             480

5 Archean         0                   0                             500
                  1 Upper             0                             510
                  4 Middle            0                             540
                  7 Lower             0                             570

Unknown                                                             *** 

Total                                                               80