geo 8 - Geological Definitions Anaerobic containing very...

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Geological Definitions Anaerobic containing very little oxygen. Anoxia the condition of containing very little oxygen. Aragonite a mineral consisting of CaCO3. Aragonite is less stable than calcite under pressures at the surface of the Earth. Calcite precipitation is often inhibited, however, and both modern and ancient seawater are supersaturated with respect to calcite. With high enough supersaturations, aragonite can also precipitate. Aragonite is common in many modern carbonate sediments as shells and as crystals that precipitated from sea water. Archean adjective implying conditions between 2.5 billion years ago and 4.0 billion years ago. The oldest rocks are about 4.0 billion years old defining the older boundary. The younger boundary is defined by an apparent difference in geological attributes of rocks older than 2.5 billion years and younger than 2.5 billion years. These differences may be due to our incomplete knowledge of the rock record rather than to a dramatic change in the Earth. Banded Iron-formation
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geo 8 - Geological Definitions Anaerobic containing very...

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