Table 1. The stratigraphic time scale.
| Era | System or period | Series or epoch |
|---|---|---|
| Cenozoic | Quaternary | Recent |
| Pleistocene | ||
| Tertiary | Pliocene | |
| Miocene | ||
| Oligocene | ||
| Eocene | ||
| Paleocene | ||
| Mesozoic | Cretaceous | |
| Jurassic | ||
| Triassic | ||
| Paleozoic | Permian | |
| Pennsylvanian | ||
| Mississippian | ||
| Devonian | ||
| Silurian[1] | ||
| Ordovician | ||
| Cambrian | ||
| — | Precambrian |
[1]The Silurian is the only major subdivision of the stratigraphic time scale not represented in Grand Teton National Park.
We are immediately struck by the fact that all of the subdivisions of the stratigraphic time scale since the beginning of the Paleozoic are compressed into the last 5 inches of our yardstick! All of the other 31 inches represent Precambrian time. We also see that subdivisions of the stratigraphic time scale do not represent equal numbers of years. We use smaller and smaller subdivisions as we approach the present. (Notice the subdivisions of the Tertiary and Quaternary in [table 1] that are too small to show even in the enlarged part of [figure 19]). This is because the record of earth history is more vague and incomplete the farther back in time we go. In effect, we are very nearsighted in our view of time. This “geological myopia” becomes increasingly evident throughout the remainder of this booklet.
Figure 19. The geologic time scale—our yardstick in time.
| ABSOLUTE TIME (Years ago) | INCHES | STRATIGRAPHIC TIME SCALE |
|---|---|---|
| First man → | 0 | CENOZOIC |
| 1 | MESOZOIC | |
| First dinosaurs → | 2 | PALEOZOIC |
| 3 | ||
| 500 million | 4 | |
| First abundant fossils → | 5 | PRECAMBRIAN |
| 6 | ||
| 7 | ||
| 1 billion | 8 | |
| 9 | ||
| 10 | ||
| 11 | ||
| 12 | ||
| 13 | ||
| 14 | ||
| Oldest known fossils → | 15 | |
| 2 billion | 16 | |
| 17 | ||
| 18 | ||
| 19 | ||
| 20 | ||
| 21 | ||
| 22 | ||
| 23 | ||
| 3 billion | 24 | |
| 25 | ||
| 26 | ||
| 27 | ||
| Oldest dated rocks → | 28 | |
| 29 | ||
| 30 | ||
| 31 | ||
| 4 billion | 32 | |
| 33 | ||
| 34 | ||
| 35 | ||
| Minimum age of the earth → | 36 |
| ENLARGEMENT OF THE LAST SIX INCHES | ||||
|---|---|---|---|---|
| ABSOLUTE TIME (Years Ago) | INCHES | STRATIGRAPHIC TIME SCALE | ||
| 0 | 0 | CENOZOIC | QUATERNARY | |
| TERTIARY | ||||
| MESOZOIC | CRETACEOUS | |||
| 1 | JURASSIC | |||
| TRIASSIC | ||||
| 2 | PALEOZOIC | PERMIAN | ||
| PENNSYLVANIAN | ||||
| MISSISSIPPIAN | ||||
| 3 | DEVONIAN | |||
| SILURIAN | ||||
| ORDOVICIAN | ||||
| 500 million | 4 | CAMBRIAN | ||
| 5 | PRECAMBRIAN | |||
| 6 | ||||
PRECAMBRIAN ROCKS—THE CORE OF THE TETONS
The visitor who looks at the high, rugged peaks of the Teton Range is seeing rocks that record about seven-eighths of all geologic time. These Precambrian rocks are part of the very foundation of the continent and are therefore commonly referred to by geologists as basement rocks. In attempting to decipher their origin and history we peer backward through the dim mists of time, piecing together scattered clues to events that occurred billions of years ago, perhaps during the very birth of the North American Continent. To cite an oft-quoted example, it is as though we were attempting to read the history of an ancient and long-forgotten civilization from the scattered unnumbered pages of a torn manuscript, written in a language that we only partially understand.