The Grand Canyon - Geologic History
• Named layers = formations and groups
• Formations = basic unit of stratigraphy
• What is stratigraphy?
The Grand Canyon - stratigraphy
• Stratigraphy - studying the rock layers in the context of time and space
• Time = vertical stacking
– Relative and numerical principles
• Space = horizontal patterns w/i layers
– Interpret environments and trace them out
The Grand Canyon - stratigraphy
• Stratigraphy - primary tool = correlation
• Studying rocks deposited at the same time from place to place (over
a large area)
• Small area - rock types
• Large region - fossils
The Grand Canyon - stratigraphy
• Strata - not perfect recorders of earth history
• Unconformities - no record in the rock layers because of non-deposition
or erosion
The Grand Canyon - stratigraphy
• Unconformities - types
• Noncomformities
• Angular unconformities
The Grand Canyon - stratigraphy
• Unconformities - types
• Disconformities
• How do you fill in the gaps?