geo lab 1

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Woodland Community College *

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15L

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Geology

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Apr 3, 2024

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- - - - • Ill!) Exercise 1 PROCEDURE PART A Using the dating techniques discussed above, determine the sequence of geologic events repre- sented in each of the block diagrams in figure 1.6. A B A youngest C oldest + FIGURE 1.6 Block diagram exercise. (continued) C Relative Dating and Unconformities I 0 <) ooo o Oo c · o 0 c, 0 <:)o· ~-o .o (::) <::) &J o,.o .0. (:) ~o-o o ~o c:,. o • o 0 o · 1:, · CJ o"" o 0 o t,. ·0 0 o.0 () 0 0 o Q.o <::) o <::).o •<::) .o ot:,o o o .o,::io . o (:>. C 9 a•oO E .Ci,•-o•c,O <::,o p. ~- ~<:> 0 C? JO <::> 0· 0 0 'i::)0. youngest oldest s D A c youngest & e J M l, :c A F B oldest 1 · I I

Exercise 1 Relative Dating and Unconformities B - - · G:-~---_-_-_- - - - - - ---- ---- - - D I. i youngest p E youngest 6 I • b 14 K J" E oldest C L- oldest -- · · - · ••• ,,. • • • - ····· -~- The Grand Canyon is one of the most spectacular laboratories of historical geology in the world. Use the cross section of the eastern Grand Canyon (figure 1.7) to answer the following questions. For questions 1 through 5, indicate which principle(s) of relative dating guided you in arriving at your answers. 1. What is the oldest body of rock in the Grand Canyon? .:.. \Vhat is the oldest sedimentary layer in the Grand Canyon? l.-\W\lS~C. Principle(s) ~pe:r p,es-:i\H.'o'l\, O.Yil~\~\.. ~V-\Ul>Y\~- 3. What is the youngest Precambrian formation in the canyon? Dox Principle(s) cross-~,(~onsh\('S. Principle(s) uper p~1H-ion

• iii • • • • • • - • • • Iii Iii - - • - • :iii :iii .. ... -- Iii I@ ,M • if Exercise 1 4. What is the oldest Paleozoic formation exposed in the canyon? Principle(s) $ u ¥J~r~iA-;0'n 5. What is the name and lithology of the youngest formation? • _ . 1 V\-Cl.1 L l ~,l7o:h~,; \' ~h>in~ Principle(s) ~C\ pew--kl)'O'Si Hot1 w SURPRISE- FORMATION ........ _ ............ _._, .... ""T""'-__,_""-r-"""T"""-,r---r-'-111 (Pennsylvanian) ; .... i .... , ........... ,_~---'-'T""...,_._-r-'-T--'--r-''-r-'-r-'tl ------------ ___________ .. ------------ BUTTE CT'" (Devonian) - . Granite Schist Sandstone Shale Limestone Relative Dating and Unconformities 6. What formations comprise the Cambrian Sys- tem in this area? TtlpfA~ <Sa~J;-or,e;,,I ~t $,l,1)/U£ 1 Ma.uv l'i e. , 7. Visually trace the unconformity at the base of the Tapeats Sandstone from left (west) to right (east) across the diagram. How does the nature of the unconformity change from west to east? 4-ru, lAVIGOVltt>Y-Mil---"I CMa"'o~ (;-om °" V\.OV\ eo Vl to r-W\ i ry on J +w., w es+- 61de. _.,, c:t Y1 a~tAlctt-: UV\C-OVlt:orrnif-"'I Oh + ½ e ea.s.+- E ) • ,, COCONINO SANDSTONE ',, .. A' ·g • V _ _ _ _ _ HERMiTsHAi:E =-~ -==== o.. ===I~ - -=-.:;;;;: SUPAI G - -- & · ------------- -•-- · ------ ___ , ·------ ·------ ___ , -------------------- fl) .___._ ........... ..&...p...14 fl) ............. -r-L...rl j ---------~- ----------~~~--~ ---------- •••• FIGURE 1.7 Geological relationships in the eastern portion of the Grand Canyon, Arizona.

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Exercise 1 8. What Paleozoic Systems are not represented in the Grand Canyon? 9. Briefly discuss the nature of the Devonian Sys- tem in this region in terms of its regional extent, lithology, and history. _, '.)1 10. What was occurring in this area during the Mis- sissippian Period? ) 11 v../ 'e_i;r l .... ) Relative Dating and Unconformities 13. Briefly outline the geological history of the Grand Canyon from Precambrian time until now based upon the patterns revealed in figure 1.7. ' I rr ' ) . 14. Which unconformity depicted in figure 1.7 rep- resents the greatest hiatus (most complex and prolonged sequence of geological processes) in the Grand Canyon? Explain your answer in terms of the processes involved with the pro- duction of these types of unconformities. I I ; . /' . t '(0 f I '- . ' '" ( • '') ~( (_t C 6 r ! f 1 U. e fo' 1 C,()_, ( t 'J '{) ': • C i1_ \ I t;' ir' f 11. What is the nature of the boundary between the Redwall Limestone and the Supai Group? l I 'r,' ' V !.-01 (I 1 ' l(.'•C 1 12. What was happening geologically in the Grand Canyon during the Ordovician Period? ~., r,' r J <. lJ '•"' ,1, ')( i r I ' PROCEDURE PART C One of the best-kept secrets of the US Park Ser- vice is Grand Canyon National Monument. Located approximately 170 km downstream from Grand Canyon National Park, the monument area displays a dramatic close-up view of the Grand Canyon, sev- eral episodes of faulting, and a spectacular display of recent as well as ancient volcanic activity, includ- ing a lava cascade that spilled into the Grand Can- yon adjacent to Vulcan's Throne and is preserved now as a frozen lava fall. At this location, it is possible to apply the rules of relative dating to reconstruct the local geologic history with great clarity. Superposition and cross- cutting relations are clearly illustrated by the geo- logic relationships that can be observed in the rocks of the monument area. -•• 11n •- ·

; • • • i i i j ii ij ii • ii ii • it ij ii ii ii iii - @ - ,I! tie ,ii! ...... ,.._~l/~IJIJl.JllttmufflitHfilliUHllilHSl1ffl~UlUW. Exercise 1 Figure 1.8 illustrates, in (A) photo, (B) sketch, and (C) cross section, the rocks in the immedi- ate vicinity of Vulcan's Throne at Grand Canyon National Monument. Study the photograph and the two line drawings of the area and answer the following questions. 1. Using superposition and cross-cutting relations, establish the proper chronologic sequence for the following list of topographic/geologic fea- tures seen in this area: Erosion of Grand Canyon C ( CJl (o Erosion of ancient Toroweap Valley e;,,.{ f-c.,,,,..- 7 • Basalt cascades w,(6~ rQcr:J,'r Deposition of Supai Formation ½ Deposition of Muav Limestone · 7\ Deposition of Red wall Limestone l1 Deposition of Temple Butte Formation i Most recent eruption of Vulcan's Turon~ I "1 Early displacement of Toroweap hw1!. :- · 13 \ Late displacement of Torowcvp :- r/'. Deposition of Bright Angel Sk,li: 8 Basalt filling ancient Torm~.1c,:p \!":'_ · :,~:- ' · l ~- Lava dams (remnants of whK~, :\r:. • v'..:- · ?:1 ·:d~ against the lower walls of ermyc,1. '..?:.l;~:ied. intracanyon lava flows on the cross section) 2. The elevation of the Colorado River below Vulcan's Throne is 1,675 ft. How deep was the lake behind the highest lava dam adjacent to Vulcan's Throne? Assume the lava dam was level with its remnant on the canyon wall below Vulcan's Throne. ~\00 -101~ Relative Dating and Unconformities 3. What is the total displacement of the Toroweap Fault in this area? L-l l--100 - LtoOO -- 400+-~- 4. What is the thickness of the lavas that have filled ancient Toroweap Valley (see figure l.8C)? 5. If the basalt at the top of ancient Toroweap Val- ley yields a radiometric date (K/Ar) of 15,000 • ,,. years, and the lowermost flows in the same val- ley yield an age of 1.2 million years, calculate the rate of b,as_alt filling in the valley (ft/my). I ) - • I ) - 0 U QJ.) ' - I ' • ~ 1 ~0c I \ 8S 600 \ 2.CLt1{::+-, l, \ 55 ,y")i = \ (o<t,6 4/ m~: -:::: \.~88 )( \o- 3 ~/~r.

geo lab 1

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