Lab 7 geologic structures and maps (1)

Problem 1. A. Number the rock layers on the geologic map surface of the block diagram B. Place strike and dip symbols on layers 3 and 4. (Use layer 2 as an example) Faults A fault is a fracture in rock along which movement has occurred. Rocks on either side of a fault are called fault blocks. There are three main types of faults: normal, reverse and strike-slip (shown in the diagrams below). If the fault plane is at an angle (that is not vertical or horizontal), the upper fault block is called the hanging wall and the lower fault block is called the footwall. In a normal fault, the hanging wall has moved down relative to the footwall. In a reverse fault, the hanging wall has moved up relative to the footwall. In a strike-slip fault, movement is horizontal. This type of fault is described as right- lateral or left-lateral based on the direction the opposite fault block appears to move when you stand facing the fault. hanging wall hanging wall N footwall footwall reverse fault normal fault left-lateral strike-slip fault \ \ ;\‘\\\ ‘\ ‘\\\\\,“ \‘\‘ 0 EEE E B B EVEVEY evewew o o o \\\ ARAEREEEEERER AT AN — — —_— — - — - e

)\ (AXAAAAAAAAAAAAAAN UUUUUUUUULULUULUUULUULULULUDULLLLLLLLLLLHHDHLLLLLLTELTY FUEVEVNNUNNUNAI A A AAAA A0 000000 e =~ Problems 2. Complete the block diagram of the fault. A. Finish numbering the layers on the right side of the fault. B Label the hanging wall and footwall C. Draw half arrows on the cross-section to show the movement of the fault blocks. D. What type of fault is this? Normal ( Reverse . Complete the block diagram of the fault A. Finish numbering the layers on the left side of the fault. B Label the hanging wall and footwall. C. Draw half arrows on the cross-section to show the movement of the fault blocks. D. What type of fault is this? Normal,, Reverse - The following diagram is a map view of a fault (you are looking down on the surface at a road broken by the fault). A. Draw half arrows on each side of the fault showing the direction of movement for that block. B. What type of fault is this? right-lateral strike-sfib) left-lateral strike-slip 5. Refer to block model #9. What type of fault is this? MAP VIEW Gealogic Structures and Maps 61

BV V. W V0 V0 VA VA VA YA A e m m e e o - J VY Y ill})“‘/i‘l‘l" » y Folds .4 when the crust is compressed (as in a ¢ onvergent plate boundary) rock layers may become folded n anticline is an arch-shaped fold. A syncline is a U shaped fold. The axis of a fold may be tilted or Plunging relative to the Earths surface. These folds are shown in the block diagrams below — plunging anticline plunging syncline In cross-section view, anticlines and synclines are easy to identify. But at the surface they appear very similar. There are two possible ways to tell them apart on geologic maps 1. The relative ages of the rock units (2 is the oldest rock on the geologic maps below) Older rocks occur at the center of an anticline Younger rocks occur at the center of a syncline, The direction rock layers are dipping Rock layers dip away from the center of an anticline. Rock layers dip toward the center of a syncline. geologic map of an antichne geologic map of a syncline geologic map of a plunging anticline geologic map of a plunging syncline F 3INg 1 s \\2 ¥ ‘ 3 3 1} i / a 3 2 3 2 3 2 1 pi A \ | : younger older younger older younger older younger Domes and basins are folds that have a circular shape on a geologic map. dome geologic map of a dome 7 N\ geologic map of a basin 7~ F 1 \\ 7

Problems 7. Identify the type of fold shown by each block model | Model 4 | Model 3 ‘ D / | N B 4 . Model 7 Onweed ‘ Model 6 » { n 1 | [ Model § e y ’ Model 8 - { | 8. A. Number the rock layers on the geologic map surface of the block diagram below. B. What type of fold is shown in the block diagram? ,:,g!( A — C. Place strike and dip symbols on the upper surface of rock layer 2. (Use layer 3 as an example). GF 5 7% 3 N 2 B. What type of fold is shown in the block diagram? mhehine C. Place strike and dip symbols on the upper surface of rock layer 2. (Use layer 3 as an example). oo /AN 64 Geologic Structures and Maps \\ 0 \\ \\ ARARA EY BN Y Y oy iy \ ARARA 0 Q0 4. A ARAIARARARARA! [ R e e g - g e e e ) - AN ARANARANAN A A EARANARA RS - - npe ififii%'

A A T “ 14. What type of stryc ture is shown on this geologic m ap? MAP VIEW 15. A. Do strike and dip symbols on this geologic map show the rock layers dipping toward or away from the center of this structure? toward (away from N B. What type of structure is this? ____ S -l C. Whichrockisyounger? {A) B MAP VIEW 16. A. What type of structure is shown on this geologic map? B. Which rock is older? (/\7 B MAP VIEW YN OYOY OO O I N W . N T Do Do BaBARARARANARARNARAIARAR AR A A M AR M B N

GEOLOGIC MAP SYMBOLS 35 D ole P P o u strike and dip fault syncline anticline plunging syncline plunging anticline 17. A. Identify the structure in the 18. A. Identify the structure in the geologic map below. geologic map below. B. Draw strike and dip symboles on the rock B. Draw the correct geologic map symbol on layers labeled A. the center of this fold. C. Draw strike and dip symbols on the younger rock layers b X v - rock younger 3 ] © MAP VIEW MAP VIEW 19. A. Draw half arrows on the cross-sectionto 20. A. Identify the structure below. show the movement of the fault blocks. Q‘)\\G\f\f« QN«\“‘M (hint: D means down, U means up) R — s B. Draw the cross-section view on the front. B. What type of fault is this? _( NG A =) 21.This geologic map shows tilted layers. What direction are the layers dipping? __ Mo Cosk MAP VIEW Geologic Structures and Maps 67

LA A A AR A AR R A AAAAAAAAAAAVYYYYY Y O T '\«l\f\'\/l:L;k;\;k:l./t)'..;uluLJLJL.J‘J.JJJ'-/J‘\J.J»J'JJ‘-JJJJ‘J v'v'vvvvvvvvvvvvv RNV VWY YYYY XYY Questions Refer to the Bedrock Geologic Map of Montgomery, Pennsylvania What Is the name of the oldest rock formation? 23. What is the name of the youngest rock formation? 24. During what geologic period ( age) did these rock formations form? 25. What ge ologic structure is shown on this map? 26. Below the surface, do the rock layers dip toward or away from the center of the fold? toward away from 27. Draw a strike and dip symbol on the Mahantango Formation (Dmbh) 28. Draw the correct geologic map symbol on the center of this fold } buvuvuvouvouuyuuvuy

Use the color Geology of Texas Map provided in class to answer the following questions 29 30 3 32 33 34, 35, 36. 37. 38. 39. 40. 41, 70 At which of the following locations would you find the youngest rock? Amarillo Midland Houston Dallas What letters are used to represent the oldest rock? _ R What is the geologic age of this rock? Pt N Precambrian Paleozoic Mesozoic Cenozoic Which of the following is a possible absolute age for this rock? 40 m.y 265 m.y. 450 m.y. ( 1500 m.y. Dinosaurs lived during the Mesozoic Era. Which location could have dinosaur fossils in rocks at the Earth’s surface? Houston Midland ;fballas Corpus Christi Observe the shape of the youngest units on the map (Qal). What is currently depositing sediment at these locations? Allvw Bryan is located on the Yegua Formation. During which geologic epoch did this form? Pliocene Miocene Oligocene @ What is the age range of this geologic period? 54 mY/ Ce1 What letters represent the Yegua Formation? _}_ C4d What is the name of the Group to the east of the Yegua Formation? (la DiN.__ Is this Group older or younger than the Yegua Formation? (Older : Younger Do rocks become older or younger if you continue to the east? Older Cfoungelx If #1 is the older rock, which diagram could represent the subsurface geology of this eastern portion of Texas? . WEST EAST WEST EAST LA S vy AN, Geologic Structures and Maps FAAA A A AR R A IR R AR NIRRT AR R R R R R T