Lecture 9a: Archean, The Proterozoic – Dawn of the Modern World (Vocabulary Flashcards)

30 vocabulary-style flashcards covering Archean–Proterozoic concepts, rocks, events, and key sites.

Archean

The eon from about 4.0 to 2.5 billion years ago characterized by the formation of early continental crust and cratons.

Proterozoic

The eon from about 2.5 Ga to 541 Ma, including Paleoproterozoic, Mesoproterozoic, and Neoproterozoic, with craton growth and oxygenation events.

Craton

A stable, ancient core of a continent that has survived multiple tectonic cycles and is often preserved as a shield.

Greenstone Belt

Archean metamorphosed volcanic–sedimentary belts; green color from metamorphism of mafic rocks; key evidence for early plate tectonics.

Granulite

High‑grade metamorphic rocks (granulite facies); part of granulite belts and remnants of early felsic crust.

Gneiss

A high‑grade metamorphic rock with banded textures formed by intense metamorphism.

Ultramafic

Rocks with very low silica and very high magnesium and iron content; sources for early crustal material.

Maf ic

Igneous rocks rich in magnesium and iron; intermediate in silica content between felsic and ultramafic.

Serpentinite

Altered ultramafic rock rich in serpentine minerals, often green, formed by hydration of mantle rocks.

Greenschist

Low‑temperature, low‑pressure metamorphic facies with minerals like chlorite and epidote; green coloration.

Abitibi Greenstone Belt

A major Archean greenstone belt in Ontario (Superior Province), ~2.8–2.6 Ga, known for gold deposits.

Huronian Glaciation

Glaciation event in Ontario around 2.4–2.2 Ga; evidence includes Gowganda Formation and non‑marine sediments.

Kenorland

An Archean supercontinent that formed in the early crustal assembly and later rifted apart.

Grenville Orogeny

Neoproterozoic to Paleozoic orogeny associated with the assembly of the Grenville belt and Laurentia.

Nuna

A Neoproterozoic supercontinent that preceded Rodinia and Laurentia in North America.

Laurentia

Ancient North American craton that became the core of the continent during supercontinent cycles.

Penokean Orogeny

Proterozoic orogenic event in North America related to accretion and collision during Nuna–Rodinia assembly.

Huronian Ocean

Early Proterozoic ocean margin associated with the opening along the North American craton.

Banded Iron Formations (BIF)

Chemical sedimentary rocks with alternating iron oxides and silica; evidence for oceanic oxygenation beginning in the Archean.

Hematite

Fe2O3; iron oxide mineral common in BIFs, contributing to red colors as iron oxidizes.

Magnetite

Fe3O4; iron oxide mineral common in BIFs, often magnetic and dark in color.

Pyrite

FeS2; iron sulfide mineral indicating anoxic Archean environments.

Great Oxygenation Event (GOE)

Global rise in atmospheric oxygen beginning in the Paleoproterozoic, with oxygenation of oceans and rocks.

Apex Chert

3.46 Ga chert in the Apex Formation (Warrawoona Group, Australia) containing some of the oldest potential fossils.

Isua

Isua Greenstone Belt in Greenland; ~3.8 Ga evidence (kerogen) for early life signatures.

Warrawoona Group

Archean rock sequence in Australia (~3.46 Ga) with early life indicators and fossil-like structures.

Pan‑Spermia

Hypothesis that life began elsewhere and was transported to Earth via meteorites or comets.

Abiogenic origin of life

Origin of life from non‑living components, preceding biological self‑replication.

Mafic dykes

Vertical intrusive sheets of mafic magma intruding surrounding rocks; evidence of early tectonic activity.

International Chronostratigraphic Chart (ICS Chart)

Global chart defining the boundaries and numerical ages of geologic time units and GSSPs.

Chert

A hard, fine‑grained sedimentary rock made of microcrystalline quartz; preserves microfossils in some Archean sites like Apex Chert.

Isua kerogen

Kerogen found in Isua rocks (~3.8 Ga) suggesting early organic material and possible biosignatures.

Huronian Ocean opening

The Proterozoic opening of an ocean margin along the North American craton.

Grenville Mountains

Mountain range formed during the Grenville Orogeny, a major Neoproterozoic event shaping eastern Laurentia.

Dykes

Magma‑filled cracks that cut across rocks; mafic dykes are common indicators of tectonic activity in the Precambrian.