The University of Texas at Austin Texas Natural Science Center Non-vertebrate Paleontology Laboratory

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Texas Geologic History

Selected Events in Texas Geologic History

Age millions of years. Uncertainties not shown*

Period

Selected Texas events

Other relevant events

Non-vertebrate activity

1.8

Quaternary

Beginning of Padre Island, the result of sea level rises due to melting glaciers.

 

Marine invertebrates in the Gulf area.

65.5

Tertiary

Volcanoes form the peaks in Big Bend.  Last movement of the Balcones fault zone during the Miocene.

Damon mound corals develop on a salt dome.

Reef building corals, many echinoids, snails, & clams.

145.5

Cretaceous

Marine conditions leave behind the limestones we see in Central Texas today.

Pilot Knob undersea volcano.

Ammonites, oysters, & rudists are abundant. Ammonites & rudists die out during the extinction at the Cretaceous-Tertiary boundary.

199.6

Jurassic

Opening of the Gulf of Mexico, salt pans develop.  These rocks are exposed at the surface only in a few places in West Texas.

Earliest flowering plants.

 

251.0

Triassic

Pangaea, the supercontinent of the time, begins to split apart.

New ferns & cycads appear.

Corals begin to expand in the west Texas marine areas.

299.0

Permian

Formation of big sponge & bryozoan reefs (the present- day Guadalupe Mountains).

Ferns of all types decline. Early conifers appear.

Brachiopods, corals, bryozoa, & crinoids decline during the Permo-Triassic extinction.

318.1

Pennsylvanian

Shallow marine environment with deltas in north Texas.

Large fern forests leave thin coal beds.

Snails, clams, crinoids, bryozoa, & trilobites in the marine areas.

359.2

Mississippian

Shallow seas, chaetetid mounds in the Llano region.

Ferns abundant.

Brachiopods, bryozoa, trilobites, & corals in the marine areas.

416.0

Devonian

Most marine rocks of this period are not exposed at  the surface today.

Ferns of all types develop in non-marine areas.

 

443.7

Silurian

West Texas shallow seas.  Very few of these rocks are  exposed at the surface today.

First land plants.

Rare occurrences of brachiopods & corals, although corals evolve rapidly during this time.

488.3

Ordovician

Limestone formed in shallow seas.  This is an important source of hydrocarbons in West Texas.

Algae/stromatolites occur around the Llano uplift.

Corals & brachiopods in the Franklin Mountains near El Paso.

542.0

Cambrian

Shallow marine conditions spread over Texas. Outcrops of these rocks can be seen around the Llano uplift.

Proliferation of life forms with hard 'skeletons'.

Trilobites roamed the seafloor, along with brachiopods, sponges, snails, & bryozoa.

2500

Proterozoic

Oldest exposed rocks in Texas, around 1.9 billion years ago.

 

Some rare algae near the Cambrian boundary.

4600

Archean

 

Simple life forms found as early as 3.5 billion years ago.

However, no such fossils have been found in Texas.


*for more details including the uncertainties of ages

 

 

Frequently used abbreviations: NPL  Non-vertebrate Paleontology Laboratory | TNSC Texas Natural Science Center | UTDGS Department of Geological Sciences | BEG  Bureau of Economic Geology | VPL Vertebrate Paleontology Laboratory | JSG  Jackson School of Geosciences | SUPPORT | VOLUNTEER | GLOSSARY


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