Ch09_Outline

Ch09_Outline - Chapter 9 Geologic Time Relative dating Law...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Chapter 9 Geologic Time Relative dating ± Law of superposition Developed by Nicolaus Steno in 1669 In an undeformed sequence of sedimentary rocks (or layered igneous rocks), the oldest rocks are on the bottom Superposition is well illustrated by the strata in the Grand Canyon Figure 9.2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Relative dating ± Principle of original horizontality Layers of sediment are generally deposited in a horizontal position Rock layers that are flat have not been disturbed ± Principle of cross-cutting relationships Younger features cut across older feature Cross-cutting relationships Figure 9.4 Relative dating ± Inclusions An inclusion is a piece of rock that is enclosed within another rock Rock containing the inclusion is younger ± Unconformity An unconformity is a break in the rock record produced by erosion and/or nondeposition of rock units
Background image of page 2
3 Relative dating ± Unconformity Types of unconformities Angular unconformity – tilted rocks are overlain by flat-lying rocks Disconformity – strata on either side of the unconformity are parallel Nonconformity – metamorphic or igneous rocks in contact with sedimentary strata Formation of an angular unconformity Figure 9.7 Unconformities in the Grand Canyon Figure 9.6
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 Fossils: Evidence of past life ± Fossil = traces or remains of prehistoric life now preserved in rock ± Fossils are generally found in sediment or sedimentary rock (rarely in metamorphic and never in igneous rock) ± Paleontology = study of fossils Fossils: Evidence of past life ± Geologically fossils are important because they Aid in interpretation of the geologic past Serve as important time indicators Allow for correlation of rocks from different places Fossils: Evidence of past life ± Types of fossils The remains of relatively recent organisms –
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 07/17/2008 for the course GS 121 taught by Professor Leavell during the Fall '07 term at Ohio State.

Page1 / 14

Ch09_Outline - Chapter 9 Geologic Time Relative dating Law...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online