Geological Time Scale Overview

Study Notes

The geological time scale is divided into eons, eras, periods, epochs, and ages.
The Precambrian is the earliest span of geological time.
The Phanerozoic eon encompasses all geological history since the Cambrian period.

Eras within the Phanerozoic:
- Paleozoic: Known as the "Age of Invertebrates."
- Mesozoic: Referred to as the "Age of Reptiles."
- Cenozoic: Called the "Age of Mammals."
Periods include:
- Paleozoic: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian.
- Mesozoic: Triassic, Jurassic, Cretaceous.
- Cenozoic: Paleogene, Neogene, Quaternary.
Epochs of the Cenozoic:
- Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene.

Cambrian Period: Early marine life; significant fossils include Haikouichthys ercaicunensis.
Ordovician Period: Rich diversity in marine life, including Nautiloid and Sea stars.
Silurian Period: First evidence of plants adapting to land, with armored fish like Dunkleosteus terrelli.
Devonian Period: Emergence of trees and land animals; notable species include Ichthyostega and Tiktaalik.
Carboniferous Period: Dominance of amphibians (e.g., Eryops) and early reptiles (e.g., Hylonomus).

Permian Period: Marked by species extinction; synapsids like Dimetrodon were prominent.
Jurassic Period: Large reptiles ruled land; appearance of birds.
Cretaceous Period: Major extinction event at its end; characterized by the breakup of the supercontinent Pangea. Notable species include early mammals like Purgatorius.

The Carboniferous Swamp ecosystem featured amphibians, large insects, and early reptiles, indicating a transition to more complex terrestrial life.
Dino-morphic animals such as Ichthyosaurus existed, showcasing the diversity of marine reptiles.
Evolutionary landmarks included the rise of tree-like plants like Archaeopteris, which contributed to the ecosystems of their time.

The current geological period is the Holocene Epoch, part of the Quaternary Period within the Cenozoic Era, showcasing recent biological and climatic developments on Earth.