The Virtual Petrified Wood Museum.  Dedicated to the Exhibition and Educational Study of Permineralized Plant Material
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Time

Nineteenth century geologists determined the relative ages of rock by studying changes in fossil assemblages. Geologist came to realize that rocks reveal an amazing story of life on Earth; different organisms have lived at different times and environments change. Furthermore, this history of life is irreversible. Thus, a relative time scale could be developed from boundaries defined by the appearance and disappearance of life forms as well as changes in rock types. The history of life on Earth was a revelation from the fossil record. This revelation would throw light on extinction and evolution. To learn more about human's evolving views of fossils and the patterns they reveal, visit the fossil section of our website.

You can use the drop down menus or the Geologic Time Scale below to navigate through different periods and epochs in our museum. Each period and epoch has an introduction that outlines some of the important biological patterns revealed by fossils. In addition to the introduction, galleries containing example fossils representative of the period or epoch may be explored.

There has been an on-going debate as to whether or not the Quaternary should be included in the timescale. Many marine geologists have argued that the Quaternary is a climato-stratigraphic unit, not a chronostratigraphic unit defined by clear markers in the rock record. Geologists who find this time period useful have come to view the Quaternary and Pleistocene as marked by the start of global cooling and glaciation 2.6 million years ago.

In 2008 the International Commission on Stratigraphy (ICS) published a timescale with the Quaternary as a full period starting at 2.6 million years ago. The Pleistocene epoch was pushed back from 1.8 to 2.6 million years ago to align with the Quaternary. The International Union of Geological Sciences (IUGS) ratified the ICS recommendation in June 2009 (Gramling, 2009, p. 13). For now, the debate as to whether or not the Quaternary should be included in the timescale seems to be settled. The following websites can be used to explore geologic time in more detail. Each site will open as a separate window.

 

Geologic Time Scale
Eon Era Period Epoch
Phanerozoic
Cenozoic
Quaternary
Holocene
Pleistocene
Neogene
Pliocene
Miocene
Paleogene
Oligocene
Eocene
Paleocene
Mesozoic
Cretaceous
Jurassic
Triassic
Paleozoic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Proterozoic
Archean
Hadean

Bibliography

Gramling, C. (2009). A Matter of Time: The Quaternary's Back. Earth, Sept.

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