Proterozoic Eon

What is the Wilson Cycle?

A model that describes the opening and closing of ocean basins and the subduction and divergence of tectonic plates during the assembly and disassembly of supercontinents

What is an orogeny?

Process of building mountains and producing other crustal deformation features over a large area

Did any orogenies occur in the Proterozoic Eon?

Yes, Grenville orogeny, Wopmay orogeny

When (in what Eon) is there the first evidence of continental glaciation?

Proterozoic Eon (2.5 – 1.6 Ga)

Is continental glaciation common over Earth's history?

Yes, 725 - 582 Ma, found in almost every continent

What is a supercontinent?

A supercontinent is a vast landmass that forms when multiple continents merge into a single, large landmass.

When (in what Eon) did the first supercontinent form?

formed about 2.1-1.8 Ga

been fully assembled ~1.74 Ga

What is the primary difference between prokaryotes and eukaryotes?

Prokaryotes don’t have a nucleus

Eukaryotes do

Which type (prokaryote or eukaryote) of organism appears first in the fossil record?

Stromatolite-forming prokaryotes

What is the primary difference between plants and animals?

Animals - heterotrophs

Plants - Autotrophs

What are metazoans?

Multicellular animals

§ More than one type of cell

§ Cells organized into tissues and organs

What is the Ediacaran Biota?

A taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period. These were enigmatic tubular and frond-shaped, mostly sessile, organisms.
Australian fossils and similar metazoans from other parts of the world

How does the Ediacaran Period relate to the Cambrian Period?

The Cambrian Period is known for the "Cambrian Explosion," during which a wide diversity of complex, multicellular life forms emerged, following the relatively simpler life forms of the Ediacaran.

What does life on Earth look like at the start of the Proterozoic era?

Life on Earth was primarily composed of simple, single-celled organisms like bacteria and archaea. There was very little oxygen in the atmosphere, and the earliest photosynthetic organisms had just begun to release oxygen as a byproduct, eventually leading to the Great Oxygenation Event.

What does life on Earth look like at the end of the Proterozoic era?

Complex, multicellular life forms, including the first animals, had emerged. The Ediacaran biota, which included a variety of soft-bodied organisms, existed during this time. These developments set the stage for the explosive diversification of life during the subsequent Cambrian Period.

Autotrophs

Produce own food

Heterotrophs

Cannot produce their own food

Aerobic

Require oxygen

Anaerobic

Do not require oxygen

Prokaryotes

§ Single-celled organisms without a nucleus

§ No membrane bound organelles

§ Reproduce asexually

§ Includes organisms that can photosynthesize

Eukaryotes

§ Single- or multi-celled organisms with a nucleus

§ Have membrane bound organelles

§ Have chromosomes

§ Reproduction method varies (sexually or asexually)

§ Includes organisms that can photosynthesize

Wilson Cycle Steps

1. Rifting of a continent (Embryonic Stage)

2. Opening of an ocean basin (Juvenile Stage)

3. Existence of an ocean basin (Mature Stage)

4. Convergence and ocean basin closure (Declining Stage)

5. Continental collision (Terminal Stage)

6. Post-closure processes (Post-Closure Stage)

Orogen

Large area showing features that result from orogeny

Day length in Proterozoic era

18 hours

Lithosphere during the Proterozoic era 2.5 – 0.541 Ga

• Mountains are built

• First supercontinent forms then breaks up

  • Continental rifts form

• Additional supercontinents form and breakup

Atmosphere and biosphere happenings Proterozoic Eon (2.5 – 0.541 Ga)

• Oxygen levels in atmosphere increase

  • Great Oxygenation Event

• First record of global glaciation

• Life continues to expand and evolve

Great Oxygenation Event

• occurs around 2.4-2.3 Ga

• Oxygen levels begin to reach significant levels in atmosphere

• Oxygen levels continue to gradually rise afterwards

• Increased oxygen leads to formation of ozone

Banded Iron Formation (BIF) deposits peak

Indicate slowly increasing oxygen levels

Rodinia

• Earliest well-documented superconNnent

• Forms about 1.1 – 0.9 Ga

• Breaks up about 0.8 – 0.6 Ga

Pannotia

• Begins to form about 0.61 Ga

• Splits apart about 0.56 Ga

First evidence of continental glaciation (Ice Age)

Tillites - Unsorted lithifies glacial debris

Varves - Thin layers of sediment that serve as a record of sediment deposition for a single year