DOCSLIB.ORG

XVI International Geological Congress Guidebook

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
XVI International Geological Congress Guidebook International Geological Congress $ V I session S 1 93 3 United tates , — Guid eb o o k 2 1 : E xcurs io n C 2 CE N T RA L O R E G O N RALPH W . CHAN E$ UNIV ERS IT$ OF CALI F ORNIA UNITED STATES $ V M T PRINTING OFFI CE GO ERN EN u WASHINGTON 193 2 T his guidebook is published under the auspices of the United States S ’ G eological urvey, but it is not a part of the Geological Survey s s x regular series of publication , and the opinions e pressed in it and the use of nomenclature do not necessarily conform to Geological Survey u sage . I I CONTENTS Page Foreword G eneral geography Geology Itinerary Bibliography ILLUSTRATIONS P LATE 1 . Map of central Oregon 2 . A B B V M Ke nzie , elknap Crater ; , iew from c Highway 3 . A x , John Day formation e posed on John Day Highway; B V M , iew northwest from the ascall ranch CE NTRAL OR EGON By RALPH W . CHANE$ FOREWORD In the preparation of this summary of the geology and paleon tology of central Oregon the writer is particularly indebted to Dr . Edwin T . Hodge , of the University of Oregon , for data regarding the history of the Cascade Mountains and the region . B uwa ld a . S to the east . Dr John P and Dr Chester tock , of the California Institute of Technology , have also furnished material of value , and the published work of Dr . Earl L . S Packard and Dr Warren D mith , of the Univers ity of Oregon , has been drawn on extensively . The studies of Dr . John C . Merriam in the John Day Basin and elsewhere in eastern 30 Oregon , which were begun more than years ago and have continued down to the present time , have served as a basis for the work of the writer in Oregon and for the preparation of this guidebook . The trip across Oregon from Eugene to Arlington traverses one of the most extensive regions in western America where continental deposits are predominant and where the record of land animals and plants during the Tertiary period is compara tivel y complete and well known . This region also represents a center of volcanic activity which has extended from the Terti ary down almost into historic times . The Cascade Range , which in its present development originated in later Tertiary time , illustrates the tectonic and volcanic history of Oregon , and its profound influence upon the life both of the Tertiary and the Recent 1 s at once apparent . S From Eugene , the site of the tate University of Oregon , in ' - et i the Willamette (wil lam ) Valley, the excurs on crosses the Oc ho co Cascade Mountains , the Madras Upland , the Moun tains , the John Day Basin , and the Columbia River Lava 1 . Plateau , as indicated on Plate GENERAL GEOGRAPH$ S mith has pointed out the twofold character of the S climate of Oregon , that in the western part of the tate being marine and that on the east side of the Cascade Range of a 1 — 1 3 14 . Numbers in parentheses refer to bibliography, pp . 2 xvr I NT E R NA TI ONA L GE O LOGI CA L CONGR E S S As continental type . regards both temperature and rainfall , these mountains act as a barrier that limits the mild moist climate to the western third of the State . Along the coast the 100 annual rainfall may exceed inches meters) , but in most of eastern Oregon it is only 1 0 to 1 5 inches to f 1 n meter) . The di ference climate between the west and the east sides of the Cascade Range is indicated by the great dis similarity of the forests in a traverse across the State . In the coastal region and from the Willamette Valley up to the crest of the mountains a dense growth of Douglas fir (P n udotruga taxzf oli a ) and associated conifers will be seen ; east of the moun tains the yellow pine (Pi n u: ponderos a ) extends for a consider able distance out on the Madras Plain , but elsewhere true forests disappear except on the summits of the Ocho co Mountains and other inland ranges ; the uplands are occupied by scattered junipers (juniperur) and sage and along the P o ul a r S alix streams there are cottonwoods ( p ) and willows ( ) . Sheep and cattle raising is the principal occupation of the rather sparse population of eastern Oregon , but excellent high ways and the extension of railroads into this part of th e State are tending to diversify the activities of its inhabitants . In western Oregon ranching of various types , fruit raising, and lu mbering are active industries , and lumbering is also impor tant along the east crest of the Cascades . GEOLOG$ — e r General f a tu er . The rocks of the Coast Range are largely i n marine sediments of Tertiary age , with basaltic and other trus ions and with intercalated flows and pyroclastic rocks . The Coast Range represents an anticlinorium , with the steepest folds on the west side and with the Willamette Valley cut into ff the soft Oligocene tufis on its eastern slopes . These tu s dip eastward under the Cascade Range and according to Hodge (14) are a part of a block or series of blocks , including much of north western Oregon , which were elevated during Pliocene time along their western edge , with perhaps a fault along the coast . Early Tertiary marine invertebrate faunas have been studied in thi s s area west of the Cascade Range, and near Goshen , a few mile south of Eugene , a lower Tertiary flora contains species whose nearest living equivalents are now found in the low latitudes of both hemispheres . The Cascade Range l n most of Oregon 1 s made up largely of the Columbia River lava , of Miocene age . This volcanic series , which reaches a maximum thickness of about feet ' e i s met rs) , rests upon the Oligocene tufis and sediments and inclined eastward across the range , farther east it is faulted down CENTRAL OR E GON 3 and extends for the most part in horizontal structure over the 14 f State and into Idaho . Hodge ( ) has urnished the following section for the Cascades l Recent : Lava flows from acidic to basic ; pyroc astics and stream deposits . : R e c Pleistocene Andesites of Cascade ang , including basaltic and andesiti 2 fl f . ows and interbedded ashes and tu fs Madras formation , torrential stream s . depo its , lake beds , and lava flows Pliocene : Erosion and deformation . : R . Miocene Columbia iver lava , basaltic flows : tufis . Oligocene Cascadia formation, a thick series of agglomerates and Eo : H of cene ighly deformed rhyolitic material , similar to Clarno formation eastern Oregon , has been found in some of the deep streams cut in the west R R side of the Cascade ange, notably at Cascadia , on the Santiam iver . East of the Cascade Range , as well as in the range itself, the Columbia River lavas are the most conspicuous and extensive series . Where there has been folding, erosion b y the larger streams has exposed the underlying rocks , as in the John Day Basin ; only along the lines of the major structural features , Ocho co such as the Mountains , have the Columbia River lavas been extensively removed . The following section is based on Merriam ’ s original section in the John Day Basin slightly B uwa ld a modified by the work of , Hodge, Packard , and the writer to include the area a djo i n ing t hi s traverse . 2 The Madras formation of Hodge includes the upper Miocene Dalles and Hood River formations of Buwa lda and Moore and the Pleistocene Deschutes . E . T . formation of Russell and Stearns See Hodge, , Framework of Cascade : 49 . 3 50 1928 R I . C . Ranges in Oregon Pan Am . Geologist, vol . , p , June, ; ussell , , 252 o : . B . Ge logy and water resources of central Oregon U S Geol Survey ull , . 90 1905 T . Des p , ; Stearns , H . , Geology and water resources of the middle - R B 63 7 . : . chutes iver asin , Oregon U S Geol Survey Water Supply Paper , p 1 3 3 w ~ 193 1 Bu ald a . P . B . N . The , ; , J , and Moore, , Dalles and Hood River for b 404 mat ons an the Columb a ve go e : Ca ne ie Inst . Wash ngton Pu . , i — d i Ri r rg r g i . 1 3 26 1930 S new . 66 . 236 . 9 1 927. p p , , and cience , ser , vol , p , Sept , 4 $ V I INTERNATIONAL GEOLOGICA L CONGRES S Geol ogi c recti on f or central Oregon Fo rmatio n Li tho logy Alluvium and terrace de posits Sand and gravel . Glacial deposi ts . Andesitic and rhyolitic f flows , dacites , and tu fs R of Cascade ange . a Sand , gravel , and lav Madras formation . flows . R k attlesna e formation . ’ Tufl , ash , and possibly Mascall formation . gravel . ’ ufi li ine basalt, t , an Columbia River lava O v d gravel . T f a s h c u f, , and rhyoliti John Day fo rma tl o n . tuff and flows . c Shale , tuff, and rhyoliti Clarno format1ou . and andesitic flows . ' ' S andstone , conglomerate , Chl co fo rm a tl o n and shale . a k fine- a ne shale P f rm a r n D r gr i d Horsetown o t o . and sandstone . Silvies River beds ; un Red impure limestone . name be s in Oc ho co d d B atholith 1 c 1 ntrus ro ns Mountains and on low ; gra no d1or1 te .
Load more

Recommended publications
  • John Day Fossil Beds National Monument
    ISSUE VIII JANUARY 2007 NARG Newsletter North America Research Group Northwest Fossil Fest Recap Last August NARG held it's first annual Northwest Fossil Fest held at INSIDE THIS ISSUE the Rice Museum in Hillsboro Oregon. The goal of the Fest was to NW Fossil Fest Recap 1 promote, educate, showcase fossils Radiocarbon Dating Fund 3 from the Pacific NW, and to have John Day Fossil Beds fun, all of which was accomplished. National Monument 3 Taxonomy Report #6 5 The tagline for the Fest is “Inspire, Inquire, Interact” and nothing What is “Fossil Search and Rescue? inspires more than displaying some of the amazing fossils specimens that Oregon Fossils have been found in the Pacific NW. Plants of the Jurassic Period 7 Tami Smith making a batch of Trilobite Cookie Many guests where surprised at the Trilobite Morphology 8 wide range of life forms that once lived where we do today. Inquiry minds want to know and we had a top-notch line up of guest speakers such as Dr. Dr. Ellen Morris Bishop, Dr. Jeffrey A. Myers, and Dr. William. N. Orr. This was a great opportunity for guest not only to learn more about the paleontology and geology of Oregon but also to meet 3 of the leading professionals in these fields. More Trilobite Cookie making There were many ways to interact, from the fossil preparation area where demonstrations took place on tools and techniques used to prepare fossils, to fossil identification, and of course all the kids activities that NARG setup. The Screen for Shark Teeth was probably the biggest hits and over 1000 Bone Valley shark teeth where given away.
    [Show full text]
  • The Geology and Mineral Resources of the John Day Region by Arthur J
    VOLUME I NUMBER 3 MARCH, 1914 THE MINERAL RESOURCES OF OREGON Published Monthly By The Oregon Bureau of Mines and Geology Small'? Ranch and Field's Mountain on John Day River. CONTENTS. The Geology and Mineral Resources of the John Day Region by Arthur J. Collier Entered aa second clam matter at Corvallis, Ore. on Feb 10, 1914, according to the Act of Aug. 24, 1912. OREGON BUREAU OF MINES AND GEOLOGY COMMISSION Omci or THE COMMISSION tit YEON BUILDING, PORTLAND, OREGON Omci or THE DlHECTOB CORVALLI8. OREGON OSWALD WEST, Governor STAFF COMMISSION HENBT M. PARES, Director ARTHUR M. SWABTLET, Mining Eng'r H. N. LAWBIE, Portland IRA A. WILLIAMS, Ceramist W. C. Fraxows, VVhitney SIDNEY W. FRENCH, Metallurgist I. ¥ RSDDT, Medford C. T. PBALL, Ontario FIELD PARTY CHIEFS T. 8. MANN, Portland P. L. CAMPBELL, Eugene A. N. WlNCHBLL W. J. KERB, Corvallis U. 8. GBAHT A J. COLLIEB SOLON SHEDD GSOBOB D. LOUDBBBACE VOLUME I NUMBER 3 MARCH, 1914 THE MINERAL RESOURCES OF OREGON A Periodical Devoted to the Development of all her Minerals PUBLISHED MONTHLY AT CORVALLIS BY THE OREGON BUREAU OF MINES AND GEOLOGY H. M. PARKS, Director *THE GEOLOGY AND MINERAL RESOURCES OF THE JOHN DAY REGION. By Arthur J. Collier. The John Day river basin in the north central part of Oregon has been for many years a favorite place for geologic exploration, on account of the occurrence there of vertebrate fossils. In recent years, however, attention has been further directed to this region from time to time by reports of the discovery of coal, oil, gas and other mineral resources.
    [Show full text]
  • John Day Fossil Beds NM: Geology and Paleoenvironments of the Clarno Unit
    John Day Fossil Beds NM: Geology and Paleoenvironments of the Clarno Unit JOHN DAY FOSSIL BEDS Geology and Paleoenvironments of the Clarno Unit John Day Fossil Beds National Monument, Oregon GEOLOGY AND PALEOENVIRONMENTS OF THE CLARNO UNIT John Day Fossil Beds National Monument, Oregon By Erick A. Bestland, PhD Erick Bestland and Associates, 1010 Monroe St., Eugene, OR 97402 Gregory J. Retallack, PhD Department of Geological Sciences University of Oregon Eugene, OR 7403-1272 June 28, 1994 Final Report NPS Contract CX-9000-1-10009 TABLE OF CONTENTS joda/bestland-retallack1/index.htm Last Updated: 21-Aug-2007 http://www.nps.gov/history/history/online_books/joda/bestland-retallack1/index.htm[4/18/2014 12:20:25 PM] John Day Fossil Beds NM: Geology and Paleoenvironments of the Clarno Unit (Table of Contents) JOHN DAY FOSSIL BEDS Geology and Paleoenvironments of the Clarno Unit John Day Fossil Beds National Monument, Oregon TABLE OF CONTENTS COVER ABSTRACT ACKNOWLEDGEMENTS CHAPTER I: INTRODUCTION AND REGIONAL GEOLOGY INTRODUCTION PREVIOUS WORK AND REGIONAL GEOLOGY Basement rocks Clarno Formation John Day Formation CHAPTER II: GEOLOGIC FRAMEWORK INTRODUCTION Stratigraphic nomenclature Radiometric age determinations CLARNO FORMATION LITHOSTRATIGRAPHIC UNITS Lower Clarno Formation units Main section JOHN DAY FORMATION LITHOSTRATIGRAPHIC UNITS Lower Big Basin Member Middle and upper Big Basin Member Turtle Cove Member GEOCHEMISTRY OF LAVA FLOW AND TUFF UNITS Basaltic lava flows Geochemistry of andesitic units Geochemistry of tuffs STRUCTURE OF CLARNO
    [Show full text]
  • Fossil Flora of the John Day Basin, Oregon, and to Request Its Publication As a Bulletin of the Survey
    Bulletin No. 204 Series 0, Systematic Geology and Paleontology, 58 DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY CHARLES D. WALCOTT, DIRECTOR FOSSIL FLORA JOHN DAT BASIN OREGON" BY FRANK MALL KNOWLTON WASHINGTON GOVERNMENT P 11 IN TING OFFICE 1002 CONTENTS. Page. Letter of transrnittal...................................................... 7 Introduction............................................................. 9 Geographic location and topographic features .............................. 10 History of exploration in the John Day Basin.............................. 11 Geological features of the John Day Basin ................................. 14 History of geological investigation in the region ........................ 14 Pre-Cretaceous rocks ................................................. 16 Knoxville and Chico beds ............................................ 17 Clarno formation..................................................... 17 John Day series...................................................... 18 Columbia Elver lava ................................................. 19 Mascall formation .................................................... 19 Kattlesnake formation...'............................................. 19 River terraces......................................................... 20 Localities for fossil plants in the John Day Basin........................... 20 Systematic description of species........................................... 21 Species excluded from this work .........................................
    [Show full text]
  • View / Open Final Thesis-Thompson A.Pdf
    A LITHOSTRATIGRAPHIC ANALYSIS OF THE CROOKED RIVER MASCALL FORMATION, CENTRAL OREGON, USA by ALEXANDRA ELISE THOMPSON A THESIS Presented to the Department of Earth Science and the Robert D. Clark Honors College in partial fulfillment of the requirements for the degree of Bachelor of Science May 2020 An Abstract of the Thesis of Alexandra Thompson for the degree of Bachelor of Science in the Department of Earth Science to be taken May 2020. Title: A Lithostratigraphic Analysis of the Crooked River Mascall Formation, Central Oregon, USA Approved: Samantha S.B. Hopkins, PhD Primary Thesis Advisor This project presents a comprehensive lithostratigraphic record of the Middle Miocene Mascall Formation deposits of the Crooked River Basin in Central Oregon, USA. The Columbia River Basalt Group (CRBG) covered the Crooked River Basin and much of the Pacific Northwest in the middle Miocene (17-13ma), altering the landscape and ecosystem. An analysis of the depositional history of this region in the aftermath of the CRBG eruptions allows us to explore the impact of large scale basalt flows on subsequent basin evolution in a region that lacks extensive lithostratigraphic data. University of Oregon field crews have measured stratigraphic sections in several different locations across the Crooked River basin in order to quantify the differences in depositional history across the basin and reconcile stratigraphy across multiple field expeditions. The regions we have defined for a holistic representation of the region are Twin Buttes in the northwest, Cave Basin in the northeast, Hawk Rim in the southwest, South Fork of the Crooked River – West in the southwest, and South Fork of the Crooked River – East in the southeast.
    [Show full text]
  • Paleontological Resource Inventory and Monitoring, Upper Columbia Basin Network
    National Park Service U.S. Department of the Interior Upper Columbia Basin Network Paleontological Resource Inventory and Monitoring UPPER COLUMBIA BASIN NETWORK Paleontological Resource Inventory and Monitoring \ UPPER COLUMBIA BASIN NETWORK Jason P. Kenworthy Inventory and Monitoring Contractor George Washington Memorial Parkway Vincent L. Santucci Chief Ranger George Washington Memorial Parkway Michaleen McNerney Paleontological Intern Seattle, WA Kathryn Snell Paleontological Intern Seattle, WA August 2005 National Park Service, TIC #D-259 NOTE: This report provides baseline paleontological resource data to National Park Service administration and resource management staff. The report contains information regarding the location of non-renewable paleontological resources within NPS units. It is not intended for distribution to the general public. On the Cover: Well-preserved skull of the “Hagerman Horse”, Equus simplicidens , from Hagerman Fossil Beds National Monument. Equus simplicidens is the earliest, most primitive known representative of the modern horse genus Equus and the state fossil of Idaho. For more information, see page 17. Photo: NPS/Smithsonian Institution. How to cite this document: Kenworthy, J.P., V. L. Santucci, M. McNerney, and K. Snell. 2005. Paleontological Resource Inventory and Monitoring, Upper Columbia Basin Network. National Park Service TIC# D-259. TABLE OF CONTENTS INTRODUCTION ...................................................................................................................................1
    [Show full text]
  • Stratigraphy and Sedimentary Petrology of the Mascall Formation, Eastern Oregon
    AN ABSTRACT OF THE THESIS OF John L. Kuiper for the degree of MASTER OF SCIENCE in GEOLOGY presented on February 12, 1988 . Title: THE STRATIGRAPHY AND SEDIMENTARY PETROLOGY OF THE MASCALL FORMATION EASTERN, OREG17,,, Abstract approved: Redactedfor privacy Dr. Robert D. Lawrence The type section of the Mascall Formation, which islocated in the John Day Valley, is interpreted to represent a sequenceof paleosols. These fossil soils were formed on a floodplainduring the middle Miocene. The measured thickness of this section is 1340feet, and although the top of the section is truncated by anerosion surface, the original thickness was probably not much morethan 2000 feet. Sediment accumulation rates were high in thevicinity of the type section with deposits being predominantly ofthe overbank type. Minimum sediment accumulation time at the typesection is thought to have been several hundred thousand years. A concretionary horizon, which occurs within the typesection is determined to represent a significant temporal hiatus. Because of the absence of caliche in this layer and elsewhere in the typesection, and because of the occurrence of moisture-lovingplants, a wet, temperate climate is envisioned for the typesection during the middle Miocene (Barstovian). The floodplain sediments of the type section arepredominantly composed of ash which was produced by nearbysilicic volcanism. This ash was mostly washed in from thesurrounding highlands, but on occasion the floodplain was blanketed by air falldebris. Scanning electron microscopy demonstrates that this ashis of the type erupted by plinian and pelean type volcanoes. The ash has been mostly altered to clay minerals, and SEM, TEM, and XRDanalyses, show these clays to consist principally of smectite (Ca, Mg), with lesser amountsof kaolin and tubular halloysite.
    [Show full text]
  • The Geology and Mineral Resources of the John Day Region by Collier
    G. E. GooJsreed, Jr. VOLUMB I NUMBBR a MARCH, 1914 THH MINERAL RESOURCES OF OREGON PaLllaLed MontLly By TLe Oreeon Bureau of Mines and Geology Small's Ranch and Field's Mountain on John DMy River. CONTENTS. The Geology and Mineral Resources of the John Day Region by Arthur J . Collier Entered as aeoond c!IU's matter at Corvallis, Ore. on Feb. 10, 1914, oooording to the Act of Aug. 24, 1912. OREGON BUREAU OF MINES AND GEOLOGY COMMISSION OntCE 0., THE C OM.MIS8ION 526 YEON BIDLDIN G, PORTLAND, OREGON 01'1'1Cil o' TlUl Dm"ltCI'oa CORVALLIS, OREGON Oew.&.LD W~ , Governor STAFF HENBT M. PAllKII, Director COMMISSION A RTHUR M . SwARTLEY, Minin& Eng'r H . N. L.o.WlliE, Portland IRA A . WILLIAIIB, Cera mist W. C. FBLLOWB, Whitney StDNJtT W. FWONcH, Metallurgist 1. F . R.,DDT, Medford C. T . PBA.LL,Ontario FI.:LD PARTY CHIKI"a T . -8. MA.NN, Portland P . L . C.un>BIILL, Eugene A. N . WINCHBLL W. 1. KlllllB, Corvallis U. 8. GRANT A 1. CoLLISR R oLON SHEDD G:monom D . Louo:mBBA.CI. VOLUME I NUMBER 3 MARCH, 1914 THE MINERAL RESOURCES OF OREGON A Periodical Devoted to the Development of all her Minerals PUBLISHED MoNTHLY AT CoRvALLis BY THE OREGON BUREAU OF MINES AND GEOLOGY H. M. PARXS, Director *THE GEOLOGY AND MINERAL RESOURCES OF THE JOHN DAY REGION. By Arthur J. Collier. The John Day river basin in the north central part of Oregon has been for many years a favorite place for geologic exploration, on account of the occurrence there of vertebrate fossils.
    [Show full text]
  • DOGAMI Open-File Report O-02-03, Geologic Framework of the Clarno
    STATE OF OREGON DEPARTMENT OF GEOLOGY AND MINERAL INDUSTRIES Suite 965, 800 NE Oregon St., #28 Portland, Oregon 97232 OPEN-FILE REPORT O-02-03 Geologic Framework of the Clarno Unit, John Day Fossil Beds National Monument, Central Oregon By E.A. Bestland1, P.E. Hammond2, D.L.S. Blackwell1, M.A. Kays1, G.J. Retallack1, and J. Stimac1 2002 1 Department of Geological Sciences, University of Oregon, Eugene, OR 97403-1272 2 Department of Geology, Portland State University, Portland, OR 97207-0751 NOTICE The Oregon Department of Geology and Mineral Industries is publishing this paper be- cause the information furthers the mission of the Department. To facilitate timely distribu- tion of the information, this report is published as received from the authors and has not been edited to our usual standards. ii Oregon Department of Geology and Mineral Industries Open-File Report O-02-03 GEOLOGIC FRAMEWORK OF THE CLARNO UNIT, JOHN DAY FOSSIL BEDS NATIONAL MONUMENT, CENTRAL OREGON E.A. Bestland1, P.E. Hammond2, D.L.S. Blackwell1, M.A. Kays1, G.J. Retallack1, J. Stimac1 1Department of Geological Sciences, University of Oregon, Eugene OR 97403-1272 2Department of Geology, Portland State University, Portland OR 97207-07501 ABSTRACT Two major geologic events are recorded in the Above the conglomerates are thick but discontinu- Eocene-Oligocene volcaniclastic strata, volcanic flows, and ous red claystones (claystone of “Red Hill”), which record a paleosols of the Clarno Unit of the John Day Fossil Beds Na- long period of local volcanic quiescence, slow floodplain tional Monument. A major plate tectonic reorganization in aggradation, and long periods of soil formation.
    [Show full text]
  • Rattlesnake Formation, Central Oregon
    PaleoBios 26(1):21–26,26(1):21–26, MayMay 115,5, 2006 © 2006 University of California Museum of Paleontology Magnetic stratigraphy of the Upper Miocene (Hemphillian) Rattlesnake Formation, central Oregon DONALD R. PROTHERO1, JONATHAN M. HOFFMAN2, and SCOTT E. FOSS3 1Department of Geology, Occidental College, Los Angeles, CA 90041 2Department of Geology, University of Florida, Gainesville, FL 32611 3Bureau of Land Management, Utah State Offi ce, P.O. Box 45155, Salt Lake City, UT 84145 The Rattlesnake Formation near Picture Gorge in the John Day region of central Oregon consists of about 120 m of siltstones and conglomerates punctuated by several tuff beds. This formation is well known for its early Hemphillian mammals, and it was originally part of the Wood Committee’s (1941) concept of the Hemphillian. Paleomagnetic samples were collected from the type section of the Rattlesnake Formation between Rattlesnake and Cottonwood Creeks 2 km south of Picture Gorge. Samples were demagnetized with both alternating fi eld and thermal demagne- tization, and yielded a stable remanence held mainly in magnetite. After cleaning, the normal and reversed directions passed a reversal test, so the remanence is interpreted to be primary. Almost the entire section is reversed in polarity except for the basal 10 m and a single site near the top of the section. Based on 40Ar/39Ar datesdates of eithereither 77.2.2 Ma or 7.05 ± 0.01 Ma on the Rattlesnake Ash Flow Tuff near the top of the section, we correlate the section with magnetic Chrons C3Bn to C3Br2n (6.9–7.3 Ma), or late early Hemphillian in age (Hh2 of Tedford et al., 2004).
    [Show full text]
  • Magnetic Stratigraphy of the Lower Portion of the Middle Miocene Mascall Formation, Central Oregon
    PaleoBios 26(1):27–32,26(1):27–32, MayMay 115,5, 2006 © 2006 University of California Museum of Paleontology Magnetic stratigraphy of the lower portion of the middle Miocene Mascall Formation, central Oregon DONALD R. PROTHERO1, ELIZABETH DRAUS2, and SCOTT FOSS3 1Department of Geology, Occidental College, Los Angeles, CA 90041. 2Department of Geology, University of Nebraska, Lincoln, NE 68588. 3Bureau of Land Management, Utah State Offi ce, P.O. Box 45155, Salt Lake City, UT 84145 The Mascall Formation in central Oregon consists of about 350 m of volcaniclastic fl oodplain siltstones and sandstones exposed in numerous fault blocks in the John Day region of central Oregon. It yields a famous early Barstovian mam- malian fauna (part of the Wood Committee’s 1941 original concept of the Barstovian) that includes at least 33 species of mammals, as well as birds, turtles, fi sh, and freshwater gastropods. The most complete section in the type area was sampled using oriented block sampling. The samples were then subjected to both alternating fi eld demagnetization at 25, 50, and 100 Gauss, followed by thermal demagnetization at 50°C steps from 200 to 630°C. Most samples yielded a stable single component of remanence that passed a reversal test, and was held largely in magnetite with minor goethite overprints. The lower half of the section is of reversed polarity, followed by shorter magnetozones of normal, reversed, and normal polarity to the top of the section. Based on dates of 16.2±1.4 Ma at the base of the section, and 15.77± 0.07 Ma in the lower part of the section, we correlate the Mascall Formation with Chron C5Br to Chron C5Bn1n (14.8–16.0 Ma).
    [Show full text]
  • DOGAMI Bulletin 78, Bibliography of the Geology and Mineral Resources of Oregon: Fifth Supplement, January 1, 1961 to December 3
    BULLETIN 78 BIBLIOGRAPHY OF THE GEOLOGY AND MINERAL RESOURCES OF OREGON I FIFTH SUPPI .EMENTI January l, 1961 to December 1, 1970 STATE OF OREGON DEPARTMENT OF GEOLOGY AND MINERAL I,NDUSTRIES 1973 STATE OF OREGON DEPARTMENT OF GEOLOGY AND MINERAL INDUSTRIES 1069 State Office Building Portland, Oregon 97201 BULLETIN 78 BIBLIOGRAPHY of the GEOLOGY · and MINERAL RESOURCES of OREGON Fifth Suppleme nt January 1, 1961 to December 31 , 1970 Compi led by Miriam S. Roberts, Margaret L. Steere, and Caroline S. Brookhyser Oregon Department of Geology and Minera l Industries 1973 GOVERNING BOARD R. W. deWeese, Portland, Chairman William E. Mil ler, Bend STATE GEOLOGIST R. E. Corcoran CONTENTS Introduction . iii Serials cited iv Bibl iography Subject index • 113 BIBLIOGRAPHY of the GEOLOGY and MINERAL RESOURCES of OREGON Fifth Supplement 1 96 1 - 1 970 compiled by Miriam S. Roberts, Margaret L. Steere, and Caroline S. Brookhyser Introduction Bu lletin 78 is the fifth supplement to the origina l "Bibliography of the Geology and Mineral Resources of Oregon," com pi led by Ray C. Treasher and Edwin T. Hodge and published in 1936 . The fifth supplement lists publications that appeared during the ten years, 1961-1970. Severa l articles published before those dates but not listed in previous bibliographies are included because of their potential value to the researcher . As in previous bibI iographi es, this one includes theses, open-fi le reports, and other unpublished materials which may be available only in certain libraries. The first section of this bulletin contains an alphabetical listing by outhor of all citations, complete with publication data .
    [Show full text]