Page:The Journal of geology (IA journalofgeology11893univ).pdf/311
may include the Oligocene to the top of the Hempstead beds. I realize that such a proposition furnishes many points for dispute. The scale is open for correction, and the standard may be defined with greater precision. But it is offered as a working hypothesis, to aid and stimulate investigation.
Such a standard time-scale of geochronology, on the basis of the Eocene period for a time-unit or geochrone would read as follows:
| Recent | 1 | = 3. | ||
| Quaternary | ||||
| Pliocene | 1 | |||
| Miocene | ||||
| Eocene | 1 | |||
| Cretaceous | 4 | = 9. | ||
| Jurassic | 3 | |||
| Triassic | 2 | |||
| Carboniferous | 6 | = 45. | ||
| Devonian | 5 | |||
| Up. Silurian | 4 | |||
Low. Silurian
or Ordovician |
15 | |||
| Cambrian | 15 | |||
The proximity of the Eocene of the Gulf border to continental conditions now in operation, the abundance of its marine fauna for comparison with like faunas of earlier or later age and of the same or different habitats, and its inclusion of traces of land-life for correlation with other conditions, and, in general, the wide distribution of available Eocene deposits and faunas for comparative study, are reasons for calling attention of investigators to this particular field for minute investigation in perfecting the geological time-scale.
Henry S. Williams.