Index Fossils, Evolution, Biostratigraphy and the Geologic Time Scale

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

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

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

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

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

Eons Phanerozoic – “obvious life” – 530 Ma to present Proterozoic – “prototypical life” – 2.5 Ga to 530 Ma Archean – “ancient” – circa 4.6 Ga to 2.5 Ga Archean and Proterozoic comprise nearly 90% of Earth’s history!

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

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

Index Fossils and International Stratotypes Biostratigraphy and Global Politics

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

Index Fossils and the S-D Boundary Graptolites * Conodonts * Chitinozoans * Trilobites Brachiopods Cephalopods

Definition of the S-D Boundary Stratotype: Klonk, near Suchomasty, Czech Republic

S-D GSSP GSSP = Global Stratotype, Sequence and Point First appearance of Monograptus uniformis uniformis Bed 20 Klonk, Czechia