What is the Tonian Period?
The Tonian (Greek: “stretch”) period is the first geologic period of the last billion years, stretching from 1,000 million to 850 million years ago. The Tonian is the first period of the longer Neoproterozoic era, which also includes the Cryogenian and the Ediacaran. Unlike many geologic periods which come after it, the Tonian is not defined based on rock layers (stratigraphy), but radiometric dating. The Tonian period, like the rest of the Neoproterozoic, was in general a cold period. The average temperature may have been 10 °C (41 °F) colder than today, especially in continental interiors. Possible trace fossils of small metazoans, such as 1-mm nematode-like worms, have been found dating to the Tonian and even 200 million years before, in the Stenian period. Although no body cast fossils of animals date to the Tonian period, this may be because organisms were very small, soft, and fossilized poorly. Multicellular algae fossils have been recovered from the Tonian period. Other than
The Tonian (Greek: “stretch”) period is the first geologic period of the last billion years, stretching from 1,000 million to 850 million years ago. The Tonian is the first period of the longer Neoproterozoic era, which also includes the Cryogenian and the Ediacaran. Unlike many geologic periods which come after it, the Tonian is not defined based on rock layers (stratigraphy), but radiometric dating. The Tonian period, like the rest of the Neoproterozoic, was in general a cold period. The average temperature may have been 10 °C (41 °F) colder than today, especially in continental interiors. Possible trace fossils of small metazoans, such as 1-mm nematode-like worms, have been found dating to the Tonian and even 200 million years before, in the Stenian period. Although no body cast fossils of animals date to the Tonian period, this may be because organisms were very small, soft, and fossilized poorly. Multicellular algae fossils have been recovered from the Tonian period. Other than un
