Glacial Lake Missoula and the Channeled Scabland Missoula, Montana to Portland, Oregon, July 20-26, 1989 PDF
Preview Glacial Lake Missoula and the Channeled Scabland Missoula, Montana to Portland, Oregon, July 20-26, 1989
Glacial Lake Missoula and the Channeled Scabland Missoula, Montana to Portland, Oregon July 20-26, 1989 Field Trip Guidebook T310 Leader: Roy M. Breckenridge, Editor Contributors: Brian F. Atwater Victor R. Baker Roy M. Breckenridge Alan]. Busacca Richard L. Chambers Robert R. Curry Larry G. Hanson Eugene ~ Kiver Eric ~ McDonald Dale F. Stradling Richard B. ~itt, Jr. American Geophysical Union, Washington D.C. Leader: Roy M. Breckenridge Idaho Geological Survey University of Idaho Moscow, 10 83843 Copyright 1989 American Geophysical Union 2000 Florida Ave., N.W., Washington, D.C. 20009 ISBN: 0-87590-619-2 Printed in the United States of America Cov~r Portland, Oregon under a Pleistocene Missoula flood. < o CJ o CJ .......... 4- I .......... ~ CJ I > ~ I f - f , / " ( rI (' ( . ( I cAP ... -4 \----_ i NEVADA---'----'----- \ CALI,:-ORNTA------" , ! ,_ i "MT. SHASTA 0i SC1Ai00LEi i 20I0km I ~ II { MT. LASSEN , • i I Map of Glacial Lake Missoula and the Channeled Scabland. TABLE OF CONTENTS Chapter 1 Introduction 1 Roy M. Breckenridge Chapter 2 GlacialLake Missoula: SedimentaryEvidencefor Multiple Drainages 3 Richard L. Chambers and Robert R. Curry Chapter 3 Lower GlacialLakesMissoula and ClarkForkIce Dams 15 Roy M. Breckenridge Chapter 4 The Spokane Valley andNorthen], Columbia Plateau 23 Eugene P. Kiver and Dale F. Stradling with a discussion ofpaleohydrology by Victor R. Baker Chapter 5 Stratigraphic and Geomorphic Evidencefor Dozens ofLast-glacialFloods 37 Richard B. Waitt and Brian F. Atwater Chapter 6 The Grand Coulee andDryFalls 51 Victor R. Baker Chapter 7 The RecordofPre-late WISconsin Floods and Late WlSconsin FloodFeatures in the Cheney-Palouse Scabland 57 Alan J. Busacca, Eric V. McDonald, and Victor R. Baker Chapter 8 The Columbia Valley and Columbia RiverGorge 63 Larry G. Hanson with a discussion ofWallula Gap by Victor R. Baker References · · · · · . · · .. · .. · · 69 Glacial Lake Missoula and the Channeled Scabland Roy M. Breckenridge, Editor Contributors: Brian F. Atwater Victor R. Baker Roy M. Breckenridge Alan J. Busacca Richard L. Chambers Robert R. Curry Larry G. Hanson Eugene P. Kiver Eric V. McDonald Dale F. Stradling Richard B. Waitt PRODUCTION Idaho Geological Survey Moscow, Idaho Design and Layout Jennifer Pattison Hall Editorial Consultant Roger C. Stewart CHAPTER 1 INTRODUCTION Roy M. Breckenridge Idaho Geological Survey, Moscow, Idaho This field guide describes the geology of Pleistocene some of the key sites that give the trip partICIpant a glacial Lake Missoula and the Channeled Scabland of general overview of these dramatic Pleistocene events the northwestern United States. Catastrophic floods andtheirgeologicsetting. Dueto thenecessarylogistics, created by outbursts from this glacially dammed lake brevity of the field guide, and redundancy with other created the largest known floods on this planet. The published materials, the reader should consult the route of this trip, shown in Figure 1, follows the path of references for more complete descriptions and discus thewater from Missoula, Montana, through glacialLake sions as well as additional localities. In addition, we are Missoula, on past the area of ice dams in Idaho, down providing supplementary materials for members of the some of the major scabland channel systems and slack 28th International Geological Congress. water basins in Washington, and through the Columbia River Gorge to Portland, Oregon. In 1933, the Sixteenth Session of the International HISTORICAL BACKGROUND Geological Congress included an excursion into the ChanneledScablandthatwaspreparedbyJ HarlenBretz In 1923, J Harlen Bretz began a series of papers on ofthe University ofChicago. Professor Bretz'swork on the Channeled Scabland of Washington State. He the ChanneledScablandcovered over40years. Now,we described what he termed an "outrageous hypothesis" of meetin 1989on thesamesubjectto seethe evidenceand flooding on a scalemuchlarger thanpreviouslyrecorded vindication ofhiswork, and to examine new research on by geologists. Professor Bretz's ideas were disputed for this important event in Quaternary geology. years, despite his irrefutable field evidence. The contro Thisfieldguideisdividedinto chaptersbytopic. Each versy is one ofthe most famous debates in the literature chapterwas preparedby geologists currently researching of American geology. His ideas of large-scale flooding this broad geologictopic. We have attempted to include wereplacedinconflictwithuniformitarianprinciplesthen c A N A J.::.._._.. 1210 .._.._..J..._.._.._..J..._.._.._..-J.._.._.._.. -J.._.. MONTANA eattle Missoula WASHINGTON IDAHO t o 50 100 HHHHH! KILOMETERS \'. FIGURE 1 Map offield trip route for 28th International Geological Congress field trip 310: Glacial Lake Missoula and the Channeled Scabland. T310: 1 ruling the science ofgeology. After additional evidence their patience and editing, and Juergen Rheinardt for for a sourceoftheflood waterwasfound (Pardee, 1942), advice and support. For production of camera-ready Bretz's diligence incompilingevidencefinally resulted in copy, I thank Roger C. Stewart for editorial review, and his ideas becoming accepted (Bretz and others, 1965). Jennifer Pattison Hall for design and layout. Greg Baker(1973) showedhowthefloodfeatureswereformed Behrens organized a tour and geologic discussion of using quantitative modeling of the megahydraulics. GrandCouleeDamfor the28thInternationalGeological Recently, attention has also been focused on interpreta Congress. tions ofthe rhythmite sequences and the flood chronolo V.R.Baker'srecentpaleohydraulicstudiesofcataclys gy (Atwater, 1986; Waitt, 1985). mic flooding were supported by the Surficial Processes Although theconceptofthecatastrophicflooding and Program,NationalScienceFoundation,NSFGrantEAR its source is now accepted, parts of the geologic record 8805321. Jim E. O'Connor worked closely with him in are still interpreted differently. We refer to several those studies. excellentsummaries(BakerandNummedal, 1978;Baker, Thisguidebookand the 28th InternationalGeological 1981) as this guidecannot dojusticeto all aspects ofthis Congress field trip benefited from the support and remarkable story. Much ofthe new research is included cooperation of a number of agencies and institutions inthisguidebook. Manyofourstopsofferexposuresthat including: theIdaho GeologicalSurvey, theU.S. Geolog surely will prompt lively discussion and questions for ical Survey, the American Geophysical Union, Eastern scientific debate. Washington University, Washington State University, Marylhurst College, University ofCalifornia Santa Cruz, Acknowledgements University of Arizona, University of Montana, the Washington State Division of Geology and Earth Re In addition to the reviewsamongthefield tripleaders sources,AMOCOProductionCompany,theU.S.Bureau we gratefully acknowledge the following for comments of Reclamation, and the National Park Service. and reviews of parts of the field trip guide: Dave Ault, Finally, thistripwould not havebeenpossiblewithout Kurt Othberg, Gerry Richmond, James Rigby, and Keith the help of many residents in the field trip area. They Stoffel. For manuscript preparation, I thank Jeannie have provide.d the trip leaders with access and valuable Breckenridge for word-processing, Loudon Stanford for information and, perhaps more importantly, an interest design and drafting, Janet Evans andPennyHanshawfor in this research. T310: 2 CHAPTER2 GLACIALLAKE MISSOULA: SEDIMENTARYEVIDENCE FORMULTIPLE DRAINAGES Richard L. Chambers AMOCO Production Company, Tulsa, Oklahoma Robert R. Curry University of California Santa Cruz, Santa Cruz, California INTRODUCTION N 1 Periodically during the Pleistocene, a lobe of glacial I~ ice advanced down the PurcellTrench in northern Idaho ~~ ~ and dammed the Clark Fork River drainage near the ~<: ~ ~IO '5 present site of Pend Oreille Lake. The ice dam im CLARK~~ KALISPELL pounded water to the east and created glacial Lake FORK Missoula. The lake once occupied six major intermon '~~oo tane basins in western Montana. I For nearly 80 years numerous investigators have 5 endeavored to decipher the glacial history of the north THOMPSON FALLS western United States. Part of this research was an attempt to understand the complexrelationship between the glacial events, Lake Missoula and the scablands of eastern Washington. The publications which resulted from these investigations have produced some of the most acrimonious scientific debates ever recorded in the geological literature. O---HUDSON ~MISSOULA 1 LOCATION r~'& This part of the field trip guide briefly describes the !':> V OJ possible origin of the glaciolacustrine sediments, giant ~ ~ currentripples andothergeomorphicfeatures associated 16km with the rapid drainage of the former glacial Lake DSTOPS ~ 10m; Missoula. The Lake Missoula portion of the field trip begins at Missoula, Montana, and ends at Camas Prairie FIGURE 1 Map offield trip route. about 100 km northwest ofMissoula. Main access isvia Interstate90andUS93andfrom MontanaHighways200 Geologic units extend in age from Precambrian to and 382. These are all-season paved roads. Unpaved Recent, with only the Mesozoic systems missing. Ter roads will be used for short distances to access one or tiaryvolcanics arelocallywidespread,withTertiarybasin two sites (Fig. 1). sediments found within the Missoula and Bitterroot valleys (Sahinen, 1957). Pleistocene glacial and glacio lacustrine sediments are widespread. REGIONAL SETTING Drainageis to the northwest bythe ClarkFork River which flows into the Columbia River and ultimately into The field trip area lies within the Rocky Mountain the Pacific Ocean at Portland, Oregon. The Clark Fork physiographic province. Deformation during the Lara is fed by a number of tributaries, principal ofwhich are mide orogeny produced a series of north to northwest the Bitterroot and Rock Creek drainages and the Black trending mountain ranges and intermontane valleys. foot and Flathead rivers. T310: 3 ABRIEF HISTORICAL REVIEW Touchet Beds in Washington. He believed that the strikingsimilarityinnumber(40) andoverallmorphology More than 100years ago Chamberlin (1885) noted "a between these deposits was evidence for at least 40 series ofparallel watermarks ... sweeping around the jokulhlaups, or catastrophic drainages ofLake Missoula valleys ... like gigantic musical staves" in the Flathead by ice dam failure. LakeRegionofnorthwesternMontana. Hebelievedthat This review is by no means meant to be comprehen a lake had formerly occupied this region, impounded by sive or complete. Interested readers are referred to glacialicelocated in the Pend Oreille region ofnorthern other articleslisted in the references cited herein and to Idaho. Chamberlin suggested its outflow was by way of those suggested throughout the field trip. Spokane, Washington. Pardee (1910) made the first significant study of glacial Lake Missoula. He described the lake and DESCRIPTION OF TRIP ROUTE AND STOPS suggested that an ice dam was once located near the present site ofPend OreilleLake. Pardeefelt that there In an effort to avoid duplication, the site descriptions was ample evidence for at least two Lakes Missoula, the within this field guide will be as brief as possible. For first lake drained rapidly, followed by a slower second more detailed information you are referred to the 1984 drainage. He did not, however, address the question of article of Chambers. how the lake drained. In 1923, Bretz presented his catastrophic flood En Route to Stop 1: hypothesis for the origin of the "channeled scablands," a term he used to describe the severelyscrubbedbarerock InMissoula, theshorelinesonthesideofMt. Sentinel surfaces of what appeared to be drainageways in the are clearly visible. The highest, at around 1265 m lowlands of eastern Washington. With a series of artic elevation, isjustabovetheUniversity'sletter"M". Aswe les, Bretz (1925, 1928a, b, c, 1929, 1930a, 1932) staunchly drive west out of the city, you see Tertiary basin-filling defended his flood hypothesis much to the disgust ofhis gravels and silts exposed on the right (north). Precam more uniformitarian audience. The biggest flaw in his brian Belt Supergroup rocks, primarily quartzites and argument was a plausible source of water for such a argillites, make up the forested hillsides around the devastating flood, although he believed Lake Missoula Missoulabasin. Thearea ofthe airportwestofMissoula was the most likely candidate. Flint (1935, 1936, 1938) is a dissected series ofglaciallakesediments, almost flat, rebuffed Bretz and suggested instead that the scablands overlying Tertiary and Quaternary gravels. As we drop were merely theproduct ofnormalproglacialdischarges. down onto the floodplain of the Clark Fork River, we The terms "flood, catastrophic, bars and channels" were come to Frenchtown. Here Lewis and Clark, in their repulsive to Flint. 1805expeditionto establish anAmericanpresencein the TheworkofPardee(1942) finallyprovidedBretzwith great western wilderness, found a small village with his desperately needed source ofwater for the "Spokane regular street patterns and blue-eyed light-skinned flood." Pardee presented strong evidence that the ice "indians" that just happened to have French surnames! dam which had contained Lake Missoula ruptured and Those names persist today on the tribal roles. released enormous quantities of water in a very short period oftime. Hecalculated an initialdischargerate of Stop 1: Ninemile Creek, "Type" Section nearly 40 km3 (9.5 mi3 per hour. Pardee cited the ) erosionalanddepositionalfeaturesfoundalongtheClark This site represents the most completely described Fork River and within the Camas Prairie basin as section of Lake Missoula rhythmites and has been evidence for this huge rush ofwater. designated the "type" section. The Ninemile Creek site In his comprehensive review of the evidence for islocated approximately35 km (21 mi) west ofMissoula repeated catastrophicdrainages ofLake Missoula, Bretz (Fig. 1) and consists of large road and stream cut ter (1969) remarked that very little was known about the races along 1-90 near the Ninemile Creek exit. Many lakebottomsediments, exceptthattheywerevarved. He other exposures oflake bottom sediments are accessible believedan investigationofthese depositswouldprovide between Missoula and Stop 1, but none are as complete valuablecluesto thequestionofhowmanytimesthelake as the one seen at Ninemile Creek. drained and refilled. Bretz felt that an unconformity Figures 2 and3 illustrate the gross sedimentarymotif surface would separate each lake sequence. ofthe Lake Missoula bottom sediments. The25 m thick The first detailed description of the Lake Missoula section is composed of 40 well-developed small-scale bottom sediments was presented by Chambers (1971), cycles, up toseveralmetersthick. Eachcycle, orrhythm with a follow up article in 1984,which has been included ite, consistsofthebasalsiltsubfacies (light-tonedlayers), as a handout to the field trip participants. whichgrades upward into awell-formed sequence ofgla Waitt (1980) related the stratigraphic sequences ciolacustrinevarves ofthe Laminated Silt-Claysubfacies describedbyChambers(1971)totherhythmicallybedded (dark-toned layers). In general, rhythmites (1-25) in the T310: 4 FIGURE 2 View of the rhythmically bedded Lake Missoula sediment at the "type" locality. The Lake Missoula rhythmiteconsistsoftwo majorsubfacies: thesiltsubfacies(light-toned) andthelaminatedsilt-claysubfacies(dark toned). 1QEe~0n) j~o:-~E~~~o~~ ~i.Q:1)~:... e&~n;~~'0~5>co Notes 20 16.551.6 23 25 HVHD..ZLL..N(4oteems) 25 17.6 11 DVHZ.L.(7toemM) 19 36.8 25 DZ (5em) 40 68.2 24 t }Weathered 9 33 8 130.7 10 ~-.9-~oCHHl..vaLLa..srtvsteosofM 18 113.3 DVZ(C1hA2arCde0pm3a,n) 23 5977....3900 21115716....4475 33321920 f~~~-._29.0_o HHvvVHHV....LLLL....ttttoooo MMMM 80.6 34 17 22 13 34.4 28 W1~:197~G~D.SZL•.(1tt0l Mem) 7 16.5 27 :~t17teVHz.L. to M H.L. to M 16 29.4 H.L. to M 24.6 26 H.L.(t5o.M7cmr- 160. 9 32.9 .~..:.;:;..:....X-L 6 X-L 21 23.629.7 25 <~o~2~2-'DVHXZ.-LL.(2t.o3eMm) ~ DZ (3.5 em) 15 33.7 24 17 V 99.5 H.L. to M 1:.;+;:=+;: H.L. to M 57.7 5 8 19.3 14 38.3 10.9 75.3 7 4 53.3 EXPLANATION 24.2 13 36.9 H. L. Horizontal Lamination 62.1 6 36.9 M Massive (no visible structure) 3 13.7 11.5 DHZ.L.(18 em) GS Minor Channel Gravels With 12 59.5 Festoon Cross-Beds 93.7 5 44.9 X-L Ripple Cross-Laminations 2 1378..53 12.6 4 11 47.5 '.-...:...~..:...-.XHDVZ.-LL.(7toemM) FDSZ FDleasmseicaStterductZuornees With Frost 44 3 DXZ-L(1H1.L.2. em) Cracks (thickness in cm) 7.2 32.3 V Varves 9.3 '-'-'-.H.L. to M 5.6 26.3 1 .:" 18 GVS • - ° H.L. 0 Pre-Cambrian Bedrock FIGURE 3 Measured section ofthe 40 rhythmites comprising the Missoula-Ninemile basin type locality. T310: 5
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