111-42 - GY 111 Lecture Notes D. Haywick (2007-08) 1 GY 111...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
GY 111 Lecture Notes D. Haywick (2007-08) 1 GY 111 Lecture Notes Thrust Faults and the Appalachian Mountains Lecture Goals : A) Thrust Faults B) The Appalachian Mountains Reference: Press et al., 2004, Chapters 2, 6, 20; Grotzinger et al., 2007, Chapters xxx-xxx; A) Thrust Faults, Several lectures ago, we discussed the major types of faults. Two of these were dip slip faults where movement was along the dip direction of the fault plane. At the time, I hinted that there was a special class of reverse dip slip fault associated with mountain building. They are low angle reverse faults called thrust faults . Thrust faults occur when widespread compression, usually associated with convergent plate boundaries, starts to affect continental rocks. They are particularly prominent in thick sequences of sedimentary rock. To make a long story short, when sedimentary rock sequences are compressed, a series of thrust faults that dip in the direction that the stress originated from start to develop. Any rock layers that lay above the thrust fault are pushed over top the layers that lay below the thrust fault. This does two things. First of all, it "thrusts" the overlying layers up above the surface of the Earth forming linear trending mountain belts (amazingly called thrust
Background image of page 1

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

View Full DocumentRight Arrow Icon
GY 111 Lecture Notes D. Haywick (2007-08) 2 fault mountains). Seconding, it shortens the original width of the sedimentary succession. If you recall our initial lecture on deformation, shortening is a natural consequence of compressive stress, so the lateral shortening that occurs when thrust faults develop is exactly as predicted. It is, however, staggering just how much compression can occur. There are thrust faults in the Cordilleran Mountains where more than 100 km of lateral displacement has occurred. Very shortly, you will see a review film on thrust faults and mountain building that will very graphically demonstrate how this compressive process occurs. You will also learn that thrust faults are seldom isolated. They usually occur in sets. As compression continues, successive thrust faults develop. Many branch off from earlier ones. Eventually, you can get very wide mountain belts composed of nothing but thrust faults and the rocks that were faulted. The block diagrams above are from your lab manual and demonstrate just how complex the geology (and the resulting geological map) can be when thrust faulting is extensive. There are two more terms that need to be introduced at this time. If you look at the previous two diagrams (and if you pay attention to the thrust fault film you will shortly see), you will hear the terms ramp and flat applied to thrust faults. The ramp is defined as the port of a thrust fault that is relatively steep that cuts up and through sedimentary
Background image of page 2
GY 111 Lecture Notes D. Haywick (2007-08) 3 layers. The flat is the nearly horizontal part of the thrust fault where rock layers slide over top of other rock layers. Flats are frequently lost from thrust fault mountains because of
Background image of page 3

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

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/04/2012 for the course GLY 111 taught by Professor Haywick during the Fall '11 term at S. Alabama.

Page1 / 11

111-42 - GY 111 Lecture Notes D. Haywick (2007-08) 1 GY 111...

This preview shows document pages 1 - 4. Sign up to view the full document.

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