Lab 7

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School

Portland Community College *

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Course

201

Subject

Geology

Date

Apr 3, 2024

Type

pdf

Pages

7

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I • Exercise J _ Geo/o . • ,g,c Maps (8 points). Geologic maps sh • · at the surface • .A ,~;::ie distribution of rock fonnations faults and other structural features exposed age of the rock units 11 acc~mpanies the map to defin; the s~bols and colors used to indicate th e geolooic • J.v 1 any unportant t f · d ' m 0 ... maps. Refer t th . aspec so a region's geologic history can be determine uo Note that the legend ac:om e geo!ogic map 0 ~ Michigan to answer the following questions. hnportant: at the top. Pan}'lng the map 1s arranged in order from oldest to the bottom to youngeSt I. Where are th . e Youngest rocks d · • · ) expose 1n this area? What is their age (geologic period)? ( 1 point 11'1 ljO~+cwt---\w Lll?pct Y'Qtn. in -tt-u, p~1lvru,iio.n aria!, W ¼ r 4tAi bt\7(/ • .• t. · v I - 2 - Where are the oldest G 9f O'Ulp kJ \.1 Mt• ()kQAfQ.Vlf. . rocks exposed 1n this area? What is their age (geologic period)? (1 point) o\dt&r Yncks cwt -\-Vu 'lttwcx\\f\ ~t.s 'n p Y t llU'Yl b llh /tqe . 3 • S::idy th e patterns made by the rock units in the southern peninsula of Michigan. What major s ctural feature is shown? Provide reason(s) to support your answer. Hint: note the spatial3. ou!crop pattern and the age relationship between different units ( as shown by the map legend). ( 1 pomt) Tu.<_ W\Ll·\c( S1YlAL1V\Vo.l /fwt-lwL \s tk b&\Sln ~) llltrLAi -\t'U_/ v-o rJcs 1n ~)-tAL {)JIL(!J>\ MOvL L °"- cJr ccilir j u1Vl,un,--h--i (, ,w~ if v) _ lAfi~ ld o~lf rocts 1 lYL -(-iv_ OvVlJ oldif VVU!~ 4. Note the outcrop pattern of Silurian and Devonian rocks in northwest Indiana. What major structural feature is present in this area? How can you tell? Hint: note the spatial outcrop pattern and the age relationship between different units (as shown by the map legend). (1 point) ~~d< ~l ~vie e.;rL~t- 1~ Otflh c1Jvv- -rtu_ tJl ci« vu Ll<- f s ~- tJ\1 ~e#v~ VOGk=_CJV) w()tV\_ f{ , Ph ·cal Geology GEO 201 lorys! Maps and StrUctures Lab 7: Geo ig,c Page3of JO
f on in this area? How can you tell? Hint: remeinb fthe defonna I • t 1 h th er Wh t • th oldest possible age o . k units were honzon a w en ey were deposited 5. a 1s e . tall ty · the roe . ) , the principle of original honzo~ w~re deposited. ( 1 pomt 1lf 1..f .'!\.. • ,,... anddeformedsometimeaftert ey lJ he 'ft,\t \JvvOvlWwv ~nct ' \Vu, O\W~ °'-~ \jl/OJJ. V\(AF»1 -\tu \)\A .t ct • eY\ ClL~ Sc> · 1{ \,M)WIJ W~\/ vJ~ ovf~l~ °' f\-tV \)'ti\\ VT/vi- -J I • (\ v' OllvV\ '.) q_ ')<) vw l l l(/'/\ ' Use the geologic map of the Grand Canyon to answ er the following questions. . h C 1 do River had not created the Grand 6. What rock unit would be exposed at the surface if t e o ora th this unit? (1 point) Canyon? Are the rocks exposed within the Canyon older or younger an - • 1iN_, (GdGS ,\- ()JI A_ {;'2(1od NM r'1 , l\ '-(__, I · 1, ( · 1 CD,hAj<M (>Nl(__ J\i4v,l,lvtd vOut':,, .Z-·',,JL' c:-,1 ct+- &\A;Y fC\U W r,\,\,lc_\ p le vrJ JL 7. Locate the Bright Angel Fault (in the southeast portion of the map area). Is the fault dip flat (gentle) or steep? How can you tell? Hint: a gently dipping fault or contact will follow the surface topography, while a steeply dipping fault or contact cuts across (shows no relationship to) the surface topography. (I point) f\;0. ~IA[{-- J{ p (\ Jt {,lp NJlf1l, OJv\& f; l. S dtu +t> -t ¼ t Gic !μ\,Jul\ WlLl ~d tdfW\ '/\Vlfr .11cYW J .' . f' 8. What is the general dip of the rock units in the Grand Canyon area? How can t 11 _U\(fl<-d701\. Hint: examine the relationship between surface contour lines (thin gray lines)youd eh? (I point) between rock layers (thin black lines). an t e contacts 1k wl &t' f. '1~ MuVI{_ f9-t,U4L~ co~ i~s VWJlL 6W\Pvl l k,& ex,f -k i1AJ, flfa~ ik.uLt ·We Ccvttl,\ l-f1 GEO 201 Physical Geology Page 4 oifJO Lab 7: Geologic Maps and Structures
Exercise 2 - Drawing a Geologic Cross Section (8 points) Geologi,c cross sections are often included with geologic maps. A geologic cross section is a vertical slice through the earth showing the arrangement of rock units and their associated contacts underground and providing a more complete picture of the local geology. The geologic map on th e next page shows the distribution of various sedimentary rock layers where they outcrop at the surface. The line from A to B cuts perpendicular to the strike of the bedding and is an ideal place to make a cross-section revealing the geologic structure of the area. A geologic cross-section is made the same way you make a topographic profile: • Align the edge of a piece of scrap paper with the line A - B on the geologic map. At each pla~e where a geologic contact crosses the line A - B, make a tick mark. Label the different rock units on each side of the tick. • Use your piece of scratch paper to transfer the locations of contacts and names for the different rock units to the top (surface) of your cross section represented by the line A-B. • Note that the strikes and dips of the contacts at the surface are shown on the map. Use a protractor to draw in the dip angle of the contacts at the surface on your cross section. The dip needs to drawn in the correct direction and at the correct angle with the surface (represented by the horizontal line A - B). Important: the dips shown on the map were measured at the surface where the contacts between the rock layers were visible. We cannot assume that the dip angle remains constant beneath the surface. Use your protractor to draw only a short line representing the dip direction and angle. Start at the surface and extend only a short distance underground. • Notice that some formations crop out in more than one area of the map. You will need to make a reasonable interpretation about how the different outcrops of the same formation are connected beneath the surface and how the dip of their contacts change below the surface to accommodate outcrops of the same layer in different areas of the map. You may also find it helpful to draw dashed lines above the ground surface of your cross section, representing the portion of the geologic structure that has been eroded away, to help you visualize how different outcrops of the same layer are related. After completing your cross section, answer these questions: (4 points for cross section) 9. What type(s) of geologic structure(s) are shown? Be specific and explain your answer. (1 point) \\f..L 5'{'(\A,{)wr U ())ft ~~"\~Vl/L. -l OJAt\c ¼ V\tL ~-\e. Of-~ tf ~-e)1 1'vl ¾ . c~vrf'e,( ~v1d. of c0/r . . v& ~s . \ V\.. --r v~ L..(._vvN- y o-Y'\ . ri~ hf- l 0. What 1s the YOUNGEST umt shown 1n this area? Explain your reasorung. (1 point) • ~t);YJ(Y'A:ru ~ye, It ls Ct~ lA U a,f ~- h~~h_S, ?E 1 · . (1 . 11. What is the OLDEST urut s own 1n t 1s area. xp ain your reasoning. point) ClNMIL- \~ - ¾ -{, ai~~ kJeCl,lAAR ,r ,~ b<,,L(Jw Wl l~¥ . 12 _ Considering the depositional environment_ of different types of ~edimentary rocks, does this sequence record a relative sea level rise or relative sea level fall? Explain your answer. ( 1 point) I+ ~s (A Vlf,,t Or}WvL l-vviL I I I fee~lK i\A,t ~Olf O n~0 o£t, IN&j-1uV hod,N._cS GEO 201 Physical Geology 0\.,, V\;c} _ t\ltD vvtJL,JdVte,, Page 5 of I O Lab J: Gp~;~t:res D\N1' w\MM fu feet {~ I fut/,
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