1 / 16

Index Fossils: Evolution and Biostratigraphy

Index Fossils: Evolution and Biostratigraphy. Evolution. Variations exist within a population Result from mutations and other genetic accidents Some variations are advantageous Others are not Some are neutral Natural Selection works on these variations

akiva
Download Presentation

Index Fossils: Evolution and Biostratigraphy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Index Fossils: Evolution and Biostratigraphy

  2. Evolution Variations exist within a population Result from mutations and other genetic accidents Some variations are advantageous Others are not Some are neutral Natural Selection works on these variations Characteristics of population shift through time = evolution

  3. What is Natural Selection? • What phrase is commonly used to describe Natural Selection? • “Survival of the fittest” • What does it mean? • Organisms best suited to the environment survive long enough to reproduce. • Advantageous traits are passed on

  4. How do new species arise? • When accumulated variations are great enough that some individuals within the population cannot interbreed, a new species has arisen. • New species commonly arise in geographically or environmentally isolated areas. • New species and original species may exist at same time

  5. 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

  6. 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? (i.e., What makes a good index fossil?)

  7. What makes a good index fossil? • Distinctive appearance/easy to recognize • Short duration between first appearance and extinction (a.k.a. RANGE) • Widespread geographic distribution (makes correlation possible across a wide area/multiple continents)

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

  9. Mile Markers in Deep Time • Life is unique for each interval of time because of evolution and extinction • Volcanos, earthquakes, mountains, types of rocks repeat throughout history • Life does not repeat – it is directional • Therefore, we can place other Earth events in a framework based on fossils

  10. Mile Markers in Deep Time • The fossil-based framework for Earth history is known as the GEOLOGIC TIME SCALE • Units: Eras, Periods, Epochs, Ages • Boundaries between units are based on bio-events

  11. Index Fossils andInternational Stratotypes The Case of the Silurian – Devonian Boundary

  12. Dr. Ivo Chlupáč and Karlstejn

  13. Index Fossils and theSilurian - Devonian Boundary • Graptolites * • Conodonts * • Chitinozoans * • Trilobites • Brachiopods • Cephalopods

  14. Definition ofthe S-D Boundary Stratotype: Klonk, near Suchomasty, Czech Republic

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

  16. Preserving the Stratotype

More Related