Transcript Lecture 9: Geologic Time & the Geologic Time Scale

Geologic Time &
the Geologic Time
Scale
How do we make sense
out of a 1000 foot-thick
rock sequence?
Rock Units:
Supergroup
Group
Formation
Member
Bed
Time Units:
Eon
Era
Period
Epoch
Stage
Geologic Time as a Linear Progression
Geologic Time in one Hour
Hadean – Proterozoic eons
Proterozoic & Phanerozoic eons
Evolution of Life on Earth (in 1 hour)
Earth’s Geologic Time in 100 Yards
Phanerozoic Eon begins between 12 and 11 yard lines
Geologic Time as a Spiraling Line
2009 Geologic Time Scale
Subdividing 4.6 billion years into smaller, more “manageable” intervals
Phanerozoic
Cenozoic
Neogene
Eocene
Bartonian
Time vs.
Eon
Era
Period
Epoch
Age
Time-rock
Eonothem
Erathem
System
Series
Stage
Don’t mix time units with rock units!
Time
vs.
Eocene
Fossils
Late
vs. Rocks
Upper
Meaning: Late Eocene fossils are found in Upper
Eocene rocks.
So Periarchus lyelli (sand dollar) lived during the
Priabonian age and fossils occur in rocks from the
Priabonian stage.
Time-Rock and Rock-Rock Units
Time
Units
Pennsylvanian rocks in SE Kansas
What’s in a Name?
Paleozoic rocks of Europe
Western England
Evolution of Western Interior Seaway, North
America (Cretaceous Period)
Cenozoic Era –
goodbye Tertiary, hello
Paleogene/Neogene
2009
1980s
Subdivisions were based on fossil content…
If the type section for the
Ordovician is in western England,
how do we know rocks in Eastern
USA are the same age?
Stratigraphic Correlation Through…
…Relative dating and Biostratigraphy
Index fossils are:
• Common
• Widespread
• Lived during a relatively
short interval of time
Surface Geology of South Carolina