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GEOLOGIC TIME CHART
| Relative Age Dating Terminology |
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| Eonothem |
Erathem |
System |
Series |
Cities
and towns in Texas where
geologic units of different ages are located. |
| Absolute Age Dating Terminology |
Began |
| Eon |
Era |
Period |
Epoch |
years ago (in millions) |
| |
Cenozoic |
Quaternary |
Holocene (Recent) |
0.01 |
Galveston, Port Aransas |
| |
Pleistocene |
1.8 |
Brownsville, Houston |
| |
Tertiary |
Pliocene |
5.3 |
Amarillo, Beeville, Lubbock, San Diego |
| P |
Miocene |
23.7 |
Jasper, Brenham, Freer |
| h |
Oligocene |
36.6 |
| a |
Eocene |
57.8 |
Alpine, Canton, Laredo |
| n |
Paleocene |
66.4 |
Mexia, Texarkana |
| |
Mesozoic |
Cretaceous |
(See Details) |
144 |
Austin, Dallas, Sonora, Glen Rose, San Antonio, Terlingua |
| e |
| r |
Jurassic |
|
208 |
No significant exposures at the surface. |
| o |
Triassic |
|
245 |
Colorado City, Post |
| z |
Paleozoic |
Permian |
|
286 |
Abilene, Pine Springs,
Wichita Falls |
| o |
Carboniferous |
Pennsylvanian |
|
320 |
Brownwood, Graham |
| I |
Mississippian |
|
360 |
Mississippian age rocks are found near Marathon and Llano. |
| c |
Devonian |
|
408 |
Marathon: Rocks of these ages are not differentiated in Texas. |
| |
Silurian |
|
438 |
| |
Ordovician |
|
505 |
| |
Cambrian |
|
570 |
Mason |
| Proterozoic |
Precambrian |
Vendian / Ediacaran |
|
600 |
|
| |
|
2,500 |
Llano: No fossils in igneous rocks but 1.9 billion years old is cool. |
| Archean |
|
|
3,900? |
Not present in Texas. |
| Hadean |
|
|
4,6000? |
Not present in Texas. |
| Earth forms |
|
|
4,6000? |
Texas will eventually exist. |
| This chart is base on absolute age dating
techniques. Relative age dating uses chronostratigraphy to date rock
sequences and does not adhere absolutely to the time intervals listed.
The terminology for each technique is presented for comparison only.
When you look at a geologic map of Texas, the color of each
Period/System will aid in locating the cities and towns. |
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