Module 81 Geologic Time

Apuntes

Module 8: Geologic Time • Difference between relatives and absolute dating • Relative Dating (Determining age order without numbers) o Relative Dating Principles (Rules for sequencing geologic events) ▪ Principle of Superposition (Bottom layers are oldest) ▪ Principle of Original Horizontality (Layers initially horizontal) ▪ Principle of Lateral Continuity (Layers extend laterally) ▪ Principle of Cross-Cutting Relationships (Cutting features are younger) ▪ Principle of Inclusions (Included fragments are older) ▪ Principle of Fossil Succession (Fossil order reflects time) -> Also, what is an index fossil and what makes it a good index? A fossil that is used to define and identify a particular time period in geologic history. A good index fossil is widespread, abundant, easily identifiable, and limited to a short time range. o Grand Canyon Example (Illustration of relative dating) o Unconformities (Gaps in the geologic record) ▪ Nonconformity (Sedimentary over igneous/metamorphic) ▪ Disconformity (Break between parallel strata) ▪ Angular Unconformity (Sedimentary over tilted strata) o Applying Relative Dating Principles (Block diagram analysis) • Absolute Dating (Determining numerica...