Index Fossils Evolution Biostratigraphy and the Geologic Time

Index Fossils, Evolution, Biostratigraphy and the Geologic Time Scale

Bio-Events o First appearances of new species o First appearances of new higher taxa o Extinctions of species o Mass extinctions of multiple taxa o Bio-events are unique points in geologic time

Index Fossils o Some fossils are more useful than others for relative age determinations o Fossils that are most useful are called INDEX FOSSILS o What factors would maximize a fossil’s usefulness?

Index Fossils o Limited Stratigraphic Range o Widespread Geographic Distribution o Commonly Pelagic o Or, tolerant of a wide variety of environments (found in many facies)

Geologic Time Scale o Standard subdivisions of Earth’s history o A “common language” by international agreement o Bio-Events are used to subdivide Geologic Time o Stratotypes or “type examples” are designated so comparisons can be standardized

Geologic Time Scale o A hierarchy of time units o Eon n Era p Period n Epoch o Age o Boundaries are defined by bio-events

Eons o Phanerozoic – “obvious life” – 530 Ma to present o Proterozoic – “prototypical life” – 2. 5 Ga to 530 Ma o Archean – “ancient” – circa 4. 6 Ga to 2. 5 Ga o Archean and Proterozoic comprise nearly 90% of Earth’s history!

Phanerozoic Eon o Cenozoic Era – “modern life” – 65 Ma to present o Mesozoic Era – “middle life” – 248 Ma to 65 Ma o Paleozoic Era – “ancient life” – 543 Ma to 248 Ma

Learn the following (in order from oldest to youngest): o 3 Eons o 3 Eras of the Phanerozoic o All of the Periods of the Phanerozoic and the Eras to which they belong o “Picks” – numerical ages of the boundaries between Eons and between Eras

Index Fossils and International Stratotypes Biostratigraphy and Global Politics

Systems, Series, Stages o Devonian System n Upper Devonian Series p Famennian p Frasnian n Middle Devonian Series p Givetian p Eifelian n Lower Devonian p Emsian p Pragian p Lochkovian o Silurian System n Upper Silurian Series p Přídolí Stage