Interpreting Earth History: A Manual in Historical Geology [8 ed.] 1478611456, 9781478611455

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Interpreting Earth History Eighth Edition

Interpreting Earth History A Manual in Historical Geology Eighth Edition

Scott Ritter

Brigha1n Young University

Morris Petersen Brigha1n Young University

WAVEIAND

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PRESS, INC. Long G~t. Lllinois

For information about this book, contact Waveland Press, Inc.

4180 fl Route 83, Suite 101 Long Grove, fl ti0047-9580 (847) 634-0081 infOO\\'ave:land.oom \\' \V\V.\vaveland.com

Photo Credits: Exercise 1: Alexander Petrenko Exercise 1: revital/Shutterstock.com Exercise J.: Kenneth KeiferJShutterstoc:k..com Exercise 4: lee PrinceJShutterstoc:k.com Exercise 5: Raduga 11./Shutterstock.com Exercise 6: Scott ~·t Ritter Exercise 7: Berti 123/Shutterstock.com Exercise 8: Kenny Tong/Shutter-stock.com Exercise 9: ~·tic.hat Ninger/Shutterstoc:k.com Exercise 10: Vladimir Sazonov/Shutterstock.com

Exercise 11: Florin Stana/Shutterstoc:k.rom Exercise 12: \iVollerb!/Shutterstock.com Exercise 13: Joy Stein/Shutterstoc:k..com Exercise 14: LesPaJenik/Shutterstock.com Exercise 15: Matthijs \iVetterau\\•JShutterstock.com Exercise 16: Tom C rundy/Shutterstoc:k.com Exercise 17: SumikophotoJShutterstoc:k..com Exercise 18: PictureguyJShutterstoc:k..com Exercise 19: Patrick Poendl/Shutterstock.com Exercise 20: Pichugin DmitryJShutterstoc:k.com

Cop yright© 2015 by Scott M. Ritter 10-digit ISBN 1-4786-1145-6 13-digit ISBN 978-1-4786-1145-5

All rights rt~~d. No part of this book n1ay be rtprodutM, stoml in a retrittJal sys/on, or trnnsnriHed in any fam1 or by nn.v 111it'a11s toithoul pern1ission in tttrilingfron1 lllL p11bli$htr. P rin ted in the Unjted States of America

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Contents Preface

Exercise

1

Relative Dating and Unconformities Establishing Sequences of Events

Exercise

2

Rad.iomevk Ages Establishing the Absoft1e Ages of Geological Events

Exercise

3

Analyris of Sed.imentary Rocks

lf

Depositional Environments

Exercise Exercise

5

Stratigraphy Organizing the Rock and Foss.ii Record

Exercise

6

Physical Coneladon

Exercise

7

Facies Relationships and Sea-1.evel Change

Exercise

8

Fossils and Fossilization

9

Evidence of Evolution

Exercise Exercise

10

Exercise

vii

Pattttns of Evolution

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16

11

Continental Drift and Plate Tectonics

155

12

Index Fossils and Depositional

170

Exercise

Exercise

13

Interpretation of Geological Maps

203

llf

Canadian Shield and Stable Pladonn

217

24

Exercise

41

Exercise

59 78 91 119 138 143

Sequences

15

Paleoroic Orogenies of Ancestral North America

Exercise

16

Cordilleran Orogeny

Exercise

17

Phanet'OJ:oic Geology of North America

224 240 269

I\ Sunvnary of Major OEj!losirionaJ and Tecrorjc Events

Exercise

18

Cenoroic Geology

275

19

Pleistocene Glaci ation

280

20

Hominin Fossils

286

Exercise Exercise Ref«ences 291

Preface

Interprtting Earth Histor.v \Vas written to provide deeper teaming actjvities for historical geology students at the college and university level f\1aterial is organized in much the same sequence as chapters in most popular historical goology textbooks and it is expected that s tudents \viii use the explanatory text to augment, not replace, textbook content. The purpose of the manual is to provide students the opportunity to engage with goolog-ical data from a variety of sources (maps, fossils, rocks, etc.) and at a variety of scales to di.seem and explain geological patterns. Of specjal concern to instructorS is the number of exercises, time, and resources required for each Jab, and sequence of topics. E.ach lab is \vritten as a stand-alone activity so that it can be assigned in concert \\ ith the sequence of topics adopted by indi\•idual instructors. Some exercises can be done outside of the Jab as home\\·ork assignments. OtherS require aocess to rock and fossil specimens provided by the instructor and are best done in a laboratory setting. Most courses \\ ill not have time to include all of the exercises contained in this manual. The intent is to provide a \vide seJectjon of exercises from \\ hich instructors may choose depending upon their teaching style, availability of materials, and other rourSe n~ds. 1

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The eighth edition of lnl"trpreting Earth History includes many of the exeoc:ises incorporated in previous editions, but is no\v in full color. Color images enhance the student's ability to see and recognize goological patterns. It also makes it easjer to see compositional (anatomical) and textural attributes of rocks and fossils. ~Jected chapterS have been expanded to provide additional dooper learning. T\\'O exercises (14 and 17) are ne\v to this edition. Exercise 14 provides students an overview of the Precambrian history of the Canadian Shield as \\rell as insights into the development of the stable platform. Similarly, exercise 17 provides a frame"rork for understanding the stratigraphic, structural, and depositional history of North America during the Phanerozoic Eon. The modifications and improvements to this edition of lnterprtting Earth History reflect critiques by students and instructors \\ ho have found this manual to be a valuable companion to the study of historical geology. We are appreciative to all \\ ho have adopted this manual in their courses and \\ ho continue to provide constructive feedback. 1

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Scott Ritter Morris Petersen

Relative Dating and Unconformities

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Establishing Sequences of Events

Leaming Objectives After completing thLs exercise, you \Viii be able to: 1. underi.iand the differences bern·een reJative and absolute (radiometric) dating; 2. define the principles of relative dating. \vhich inc)ude original horizontality. superposition. cros.s-

cutting relationships. incJu...-ions, and fauna) succession; 3. establi'ih the o rder of geological events that conspired to form the given reJation.'ihips sho\\'n on bkx:k diagrams and images depicting geologicaJ features, as \Vell as list the principJe(s) that enabled you to establi'ih the correct order of even ls; 4. recognize the four types o f unconformities on block diagrams and images o f actual field area.s; and 5. explain the nature and reJative duration of processes that create each type of unconformity.

Introduction The discovery of "deep time'' is one of geology's greatest contributions to human understanding. The conceptual foundations laid by eighteenth- and nineteenth-century gootogists \\·orking in relatively small geographic areas paved the \vay for development of the modem high-resolution goological timescale (figure 1.1), \\1 hich spans 4.6 billion years of Earth history and applies to geological featu res any\\'here on Earth. The succession of eons, eras, and ~riods \\1 as constructed during the early part of the nineteenth century using the principles of relative dating that are the focus of this exercise. The absolute ti~cale (numerical scale) \vas added after the discovery of radioacti\•ity and the develop-

ment of techniques that \ve.rie able to reliably measure small amounts of radiogenic isotope> in gooJog-ical materials. The numerical scale, the subject of exercise 2, \\•as developed! during the latter half of the h\rentieth century.

Principles of Relative Dating ln this exercise, \\'e are con~med only \\•ith a relative sequence of goolog-ical events; that is, event A preceded event B or goological feature Bis younger than feature A, but older than feature C. To establish the correct ordei' of events, goolog-ists use five simple, but po\verful, concepts. First,. sedimentary rock layers are horizontal \\'hen first deposited. Any marked variation from the horizon-

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Exercise

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ERA PERIOD

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·fO sill has baked both the underlying and overlying strata. Inclusions of sand.'itone from layers 2 and 4 indicate th.at igneous layer 3 post-dates both of the adjacent sandstone layers.

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C The Jaw of inclusK>n.'> indicates that igneou.'> layer 3 "'as formed prior to deposition of sand.'itone layer 4.

0. A dike has intruded bed.'> 1 through 4, but is overlain (cros.'KUI) by layer 5. Jndusion.5 of the d ike rock \\•ere incorporated into the ba.c;e of sand.'itone layer 5, also indicating that the dike \Va.. intruded and partially eroded prior to deposition of layer S.

Brock diagrams showing various relationships of igneous and sedimentary rocks th.at. are useful in establishing the retative order ol evenu.

granite (light). This relationship indicates that metamorphic rocks "rere tom from the \valJ of a magma chamber and enclosed \vithin the magma as it \vas emplaced. In figure 1.38, a layer of dark igneous rock (layer 3) is located behveen hvo layerS of sand· stone. This relationship may have occurrOO in one of t\\·o \\'ays. Either the igneous layer formed as a s ur· face AO\\' subsequent to deposition of layer 2, but before deposition of layer 4, or the igneous layer \vas intruded as an igneous s ill after deposition of layers

2 and 4. A lava AO\\' and a horizontal s ill (sheet of intruded igneous material) appear similar in outcrop and on geological maps, but have quite different age relationships. The enclosure? of sandstone fragments (inclusions) of layer 4 \\·ithin igneous rocks of layer 3 indicates that layer 3 is an intrusive body emplaSi.-- 0.0625

PEBBLE COARSE MEDIUM

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Describing Clastic Sedimentary Rocks CJastic sedimentary rocks are composed of fragments (cl as-ts) of minera~ rocks, or fossils that have been transported from the site of sediment production (provenance) to the site of deposition by \\'ind, water, and/ or ice. The nature of the source ROCK NAME area, the transport history, and &SYMBOL the environment of deposition are indicated by the texture, composition, and layering of th• resulting sedimentary rock. Hence, the pr00$.S of deciphering a rock's h.istory begins " 'ith a thorough description of these CONGLOMERATE attributes. Textu.re referS to size, sorting,. and shape of a rock's constituent clasts or partides. In nature, mechanical \veathering produces particles that range in size from cJay and s ilt at one extreme to house-size bouJders at the other. By convention, geologists divide clastjc sediment into three size categories (mud, sand, and graveJ) us ing the \t\'ent" 'orth scale. Note that these ~-- ~

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duces- clay (elastic) particles t hat are carried do\vnstream in suspension as \\·e:IJ as dissociated ions that are carried in solution (chemical sediment). Clastic (or detrital) s.edimen tary rock forms \\ hen mechanically derived material is compacted and cemented in a basin of deposition. Chemi cal sedimentary roe.ks such as rock salt and limes-tone fonn \vhen chemically derived sediment carried in solution is precipitated through evaporation o r biogenic activity. These t\\·o major families of sOOi.mentary rocks will be discussed separately, beginning with dastic rocks.

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