Annotated Geologic Time Scale

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This annotated geologic time scale is presented to provide a perspective on the geological formations and events that shaped the Taos area, and the relevant mineral and fossil specimens at Taos Rockers. For the most accurate geologic time scale for North America, see the GSA (Geological Society of America) time scale

The numerical time spans of each era, period and epoch are under continuous revision by geologically small numbers of years, so you will notice slight discrepancies in the years listed in different sources.

Note that "mya" is the abbreviation for "millions of years ago."

Precambrian Era

Few fossil remains exist in rocks of this era; many of the scarce fossil flora and fauna are represented in the Ediacaran and Cryogenian periods. Organisms had not developed significant hard parts and soft tissue is rarely preserved in the fossil record

Geological features near Taos of Precambrian age:

  • The Picuris Mountains
  • The Sangre de Cristo Mountains (parts)
  • The Harding Pegmatite

Paleozoic Era 539 – 252 mya

The term paleozoic means “ancient life.” This era saw the evolutionary “explosion” of life on earth, both animal and plant forms. Most forms of life that evolved in this era are now extinct.

Near Taos:  Paleozoic age rocks in the Sangre de Cristo Mountains contain abundant fossils. These cannot be collected legally.

Cambrian Period 529 – 485 mya

This period started with the evolutionary “explosion” of life forms – both animals and plants. Most animal phyla evolved in this time period, although the modern forms may not look like their Cambrian ancestors. Some of the most notable:

Phylum Arthropoda (trilobites and others)
Phylum Brachiopoda (shelled organisms)
Phylum Echinodermata (crinoids, starfish)
Phylum Cnidaria (corals)
Phyum Mollusca (molluscs)
Phylum Porifera (sponges)
Phylum Chordata – jawless fish (Agnatha)

Ordovician Period – 485 – 444 mya

Phylum Bryozoa first appeared
The first plant life appeared on land
The first jawed fish appeared in the oceans

Silurian Period – 444 – 419 mya

Devonian Period – 419 – 359 mya

The first land animals appeared (amphibians)
The first tree-like plants appeared with vascular systems (ferns, horsetails)
The first plants with seeds appeared.


Carboniferous Period – 359 – 299 mya

The first plants with woody stems appeared
       The first gymnosperms appeared


Permian Period – 299 – 292 mya 

Mesozoic Era – 252 – 66 mya

Triassic Period – 252 – 201 mya

The first dinosaurs appeared
The first mammals appeared
The first ginkgoes and cycads appeared
“Nacimiento” petrified wood


Jurassic Period – 201 – 145 mya

The first birds appeared
The first pine trees appeared


Cretaceous Period – 145 – 66 mya

The first marsupials appeared
Carpopenaeus shrimp (about 100 mya)
The first angiosperms (flowering plants) appeared
The first maple trees appeared


Cenozoic Era – 66 mya – present

Paleogene Period – 66 – 23 mya

The first whales appeared
The first oak trees appeared56 mya – first oak trees
Fossil fish Knightia
Metasequoia occidentalis


Neogene Period – 23 – 2.6 mya

The megalodon sharks lived
Early eruptions in the Rio Grande Rift area near Taos


Quaternary Period – 2.6 mya – present

The basalt lava flows and related rift volcanoes now exposed along the Rio Grande rift were formed
The Sangre de Cristo Mountains were uplifted
The Jemez Volcano erupted the Bandolier Tuffs
True fossil amber (more than 100,000 years old)
Copal (less than 100,000 years old)