Final answer:
The 6 major geological periods in question are Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian, all part of the Paleozoic era. These periods included significant events such as the Cambrian Explosion, colonization of land by plants and vertebrates, and ended with the largest mass extinction at the end of the Permian.
Step-by-step explanation:
To know the 6 major geological transgressions and when they occurred, one must look into the geological time scale. Often, the term 'transgressions' refers to periods when sea levels rose, covering vast areas that were previously dry land. However, it may also colloquially refer to significant geological or evolutionary events related to these time frames.
The six periods from the information provided are Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. These periods are part of the Paleozoic era.
- The Cambrian Period is when complex life forms significantly diversified in an event known as the 'Cambrian Explosion' (541 to 485 million years ago or Ma).
- During the Ordovician Period, which followed the Cambrian, the first land plants appeared (>500 Ma).
- The Silurian Period, following the Ordovician, saw further development of terrestrial flora.
- The Devonian Period is when vertebrates first made significant inroads onto land.
- The Carboniferous Period is known for high atmospheric oxygen levels and the vast coal swamps that would become today's coal deposits.
The Permian Period spans from the end of the Carboniferous to the beginning of the Mesozoic era with the Triassic period (298.9 to 251.902 Ma). The end of the Permian is marked by the largest mass extinction in Earth's history.