Post on 15-Dec-2015
transcript
Primary structures and facing directions
Goal: To begin to understand how to use primary structures as markers of deformation
Quick review of Huttonian principals
• Original horizontality
• Superposition
• Cross-cutting relationships
• Inclusion
What are primary structures
• Depositional, intrusive, or volcanic contacts — Bedding probably most useful
• Sedimentary structures• Biogenic structures• Volcanic structures• Metamorphic features
Structures that form during deposition or crystallization of the rock
Why do we care
1. Serve as markers of deformation
2. Can often be used to determine facing direction or “Which way is up” or “Way up”
• Upright beds
• Overturned beds
Contacts as primary structures• Depositional or volcanic, conformable
• Intrusive
• Depositional or volcanic, unconformable• Disconformity• Angular unconformity• Nonconformity
Why is it important to know facing direction?
1. Can help interpret complicated structures from isolated outcrops
2. Can serve as a predictive tool while mapping