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 .