Maps and Cross Sections Flashcards
What is the difference between a map and a cross section?
Map: A plan view of the distribution of rock types
Cross section: A vertical section illustrating the changes in rock type with increasing depth
What is the law of original horizontality?
Sedimentary rocks are laid down horizontally
What is the law of superpositon?
Originally, younger rocks are laid on top of older rocks
When does folding occur?
After rocks have been deposited
When do igneous intrusions happen?
After the formation of the surrounding rocks
What do unconformities represent?
Gaps which are caused by periods of erosion
What are the four types of unconformities?
Angular unconformity
Nonconformity
Disconformity
Paraconformity
What is an angular unconformity?
An unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers
What is a nonconformity?
Exists between sedimentary and metamorphic or igneous rocks, with the igneous/metamorphic under the break
What is a disconformity?
An unconformity between parallel layers where there is only erosion (no tilting) and the bedding stays parallel either side of the break
Describe a paraconformity.
- Parallel strata above and below break
- Very short time gap
- Very little apparent erosion
- Break resembles a bedding plane
What are 2 other terms for a paraconformity?
Non-depositional unconformity, pseudoconformity
What types of igneous formations cross cut the bedding?
Dykes, Batholiths, Volcanic pipes
What types of igneous formations are parallel to bedding (concordant)?
Lava flows, Pyroclastic flows, Sills
Is a dyke an intrusion or an extrusion?
Extrusion
