CONIFER DOMINANTS IN THE MIDDLE TERTIARY OF THE JOHN DAY BASIN, OREGON

RALPH w. CHANEY Professor of Palaeontology, University of California, and Research Associate, Carnegie Institution o[ Washington

FOREWORD _ During the past few years, most of my time has been devoted to a re-study of all URING the early weeks of 1948, the available material of Sequoia and it was my good fortune to be in Taxodium from the Cretaceous and Tertiary D daily contact with Birbal Sahni who of North America. Many of the fossil was then a visitor at the University of specimens previously assigned to these California. We had many discussions of genera are now known to represen t M eta­ Metasequoia, the conifer whose discovery sequoia. The characters by which the in Asia a few years before was proving of leaves and cones of this genus, both living such great interest to botanists and palaeo­ and fossil, may be recognized have been botanists. My departure for central China considered by Miki, Hu and Cheng, Stebbins in February to visit scattered groves of ( 1948, p. 96), and Chaney ( 1948, p. 509; this survivor from the past brought to a 1951, pp. 174-181, PL. 6). It will b~suffi­ close an enjoyable and profitable opportunity cient at this point to note that a decussate to consider problems of Indian and North arrangement is characteristic of Metasequoia, American palaeobotany with a leading stu­ by which foliage shoots and needles and dent of science in Asia. I shall always be cones, both pistillate and staminate, may be happy to recall that on the night of my readily distinguished from those of Sequoia departure from San Francisco, Dr. and Mrs. and Taxodium, in which the arrangement Sahni came to the airport to wish me fare­ is spiral. Since phyllotaxy and cone-scale well on my journey across the Pacific. position are readily observable on well­ preserved fossil material, no difficulty is INTRODUCTION experienced in separating Tertiary specimens of Metasequoia from those of related genera The discovery of Metasequoia during of the Taxodiaceae. the past decade has made necessary an With the hope of reaching a fuller under­ extensive revision of our concepts regarding standing of the nature of the past environ­ the Tertiary forests of western North ments occupied by the trees of these three America. Miki's assignment of certain genera, field studies have been carried on leaves and cones from the Pliocene of in China under the auspices of the Save­ Japan to Metasequoia (1941, p. 261) the-Redwoods League, and in the United at once raised the question whether other State, with the aid of grants from the fossil specimens previously considered to Carnegie Institution of Washington, the represent Sequo£a might not also be refer­ American Philosophical Society and the able to this new genus. In 1944 living University of California. The results of trees of Metasequoia were found surviving these studies will here be considered in in central China, and their recognition relation to the plant record from the John and description by Hu and Cheng (1948, Day Basin of eastern Oregon, a region p. 153) has provided a basis for interpret­ which provides an exceptionally complete ing with increasing discernment the many sequence of Tertiary floral units (CHANEY, fossil floras in which this genus is represented. 1938, p. 633). The Clarno flora, assigned Unlike Sequoia, whose habit in past time as to the Middle and Upper Eocene, is made today appears to have been evergreen, Meta­ up largely of evergreen angiosperms of sequoia glyptostroboides Hu and Cheng is a subtropical types; remains of conifers are deciduous tree. In this respect it resembles rare, and all available specimens appear to the swamp cypress, Taxodium distichum be referable to Glyptostrobus. In the lower Richard, of the south-eastern United States. part of the overlying John Day formation, 106 THE PALAEOBOTA)fossils of tem­ ages, are indicative of deposition in quiet perate types which appear to have been water, probably after only local trans­ predominantly deciduous in habit. Among porta tion. These layers of leaf shales reach the most numerous of t.hese are the leafy a maximum thickness of two or three feet, shoots and cones of a tree which has for and are limited in horizontal extent to a many years been considered to represent few scores of feet. They appear to have Sequoia langsdorfii (Brongniart) Heer. This accumulated along stream courses in a species was correctly described by Heer region of moderate relief, for they and from the Miocene of Switzerland (1855, associated sediments are predominantly fine p. 54). but its subsequent recognition textured ( PL. 4, FIG. 9). at scores of localities at middle and high Impressions of leaves and fruits of this latitudes outside of western Europe was Upper Oligocene flora have been found in based in most cases upon incorrect identi­ abundance at four localities in the John fications. The record of its presence in Day Basin (PL. 1), and silicified wood is the John Day formation is in this category, also of wide occurrence. Similar plant fos­ for all of the leafy shoots and cones assigned sils have been studied by the writer in the to 5. langsdorfii show the decussate arrange­ Crooked River Basin to the south (1927, ment of Metasequoia, and are now assigned p. 45), and at localities in western Ore­ to M. occidentalis (Newberry) Chaney gon (1938, p. 640). The original locality (CHANEY, 1951, p. 225). In the Mascall on Bridge Creek, nine miles north-west of formation, whose age is considered to be Mitchell, has been most extensively studied Middle Miocene, the most abundant conifer (CHANEY, 1925, p. 4) and we shall follow is Taxodium dubium1 (Sternberg) Heer. a custom of long standing in referring all The uppermost sedimentary member of the of the fossil plants from the Lower J oh n section, the Pliocene Rattlesnake formation, Day formation to the Bridge Creek flora. contains a small flora recently discovered by Table I gives the numerical representation Wilkinson (CHANEY, 1948, p. 1367); no of the most abundant species of the Bridge conifers have as yet been found in this flora, Creek flora as based upon leaf counts of which is characterized by deciduous angio­ thirty thousand specimens. 2 From this table sperms of riparian types. Our present dis­ is omitted one abundant species of uncertain cussion will be confined to floras from the taxonomic status, represented by 1823 leaves Lower John Day and Mascall formations. or leaflets making up six per cent of the total; originally described as Fraxinus inte­ COMPOSITION AND RELATIONS OF THE grifolia Newberry, and later as Umbellularia BRIDGE CREEK FLORA oregonensis ( Knowlton & Cockerell) Chaney, this material has not yet been satisfactorily The John Day formation was laid down identified, though it may, in part, represent during a time of relative quiescence, follow­ the foliage of a legume, as suggested by ing outpouring of lava and accumulation of Brown. coarse tuffs and mudflows which character­ It is difficult to distinguish between many ized the preceding Clarno stage (WIL­ of the leaf impressions of Alnus carpinoides LIAMS, 1948, p. 23). Its deposition was and Betula heteromorpha, and the representa­ completed before the Middle Miocene, during tion of these two species is here combined. which time there accumulated flows of The latter appears to be the more abundant, Columbia River Basalt with a thickness and the two species make up nearly half reaching 2,500 ft. in eastern Oregon. of the specimens counted. Metasequoia However, vulcanism may be considered to occidentalis is another abundant species, have continued during much of the inter­ and at the Twickenham locality makes up vening John Day stage; the plant-bearing seventy-nine per cent of the florule. In layers in the Lower John Day formation addition to the ten species represen ted by are largely made up of volcanic ash; their one per cent or more, and constituting finely bedded character, and the presence nine-tenths of the specimens counted, addi­ tional species are included for comparison I. A study of the Masca,lI flora by the writer in association with D. 1. Axelrod is now in an ad­ 2. For discussion of the method followed in these vanced stage. quantitative studies, see Chaney, 1924, p. 127. CHAKEY - COXIFER DOMli'\AC'"TS OF THE JOH):" DAY BASI=' 107

TABLE 1- THE NUMERICAL REPRESENTATION OF COMMON SPECIES

BRIDGE CREP:J< ~fASCAU. -----' -., A.- Number 01 Total. ='lumber of Tot-ai, ~peci.mens Q, Q, Q sperimens ,.

Gi"kgo adiontoidts (Unger) Heer 0 214 2 !\1dasequoia oaiMntahs (Newberry) Chaney 8,20.; 27 228. . 2 Taxodr:l4.m dubium (Sternberg) Heer ~l 3A26 34 Carya bt..ndirei ( Lesquereux) Chaney & A~elrorl 0 1,060 11 Betula and Alnus 13,566 46 12'-) I Carpinus grandis Unger 740 2 0 Ostrya O1'CeoH1:ana Chancy 8 26 Qlurcus spp. 2,743 9 2,028 20 Small, unlobed spp. 2,743 9 Oa I Q'tUCUS cons,:milis Newberry 1,855 6 0 QI4CfCUS darnensis Trelease 824 3 0 QUCfCltS daya.na Knowlton 0 95 1 Large, lobed spp. 0 1,933 19 QuerclH pseudo·lyraJa. Lesquereux 0 1,.i98 16 2;)3 Qu.ercus merriami Knowlton 0 ., 3 Ulmus SpfC1.oSa Newberry 642 :20.) 2 Ulntl4.s pauc1:denJaj.Q H. V. Smith 0 142 1 Ccrcidiphyllum crcnatum ( Unger) Brown 485 2 n PlaJanus dissecla LcsQuereu x 246 I 354 Cedrda merrilli (Chaney) Bro\\'o 10 0 Cedrela trainti Arnold 0 J!l!l 2 AUT spp. 2,;1 I 1;67 7 AUT ;:labroidefl Brown ~:il I 16 A af bola,ui~,iLesquereux 0 230 2 Acer negundoides MacGinitie .; 20.) 2 Acer sco:tiae MacGinitie 0 124 I with the Mascall flora in the lists of origin, though such other species as M ahonia Table 1. Other species rare in our collec­ simplex (Newberry) Arnold, and possibly tions but significant in this discussion are: Philadelphus bendirei (Knowlton) Chaney Ailanthus ovata Lesquereux, Castanea orien­ may also have come up from the sonth. talis Chaney, Celtis obliquifolia Chaney, Fourteen of the Bridge Creek plants are Comus ovalis Lesquereux, Fagus pacifica generically represented in the Fushun flora Chaney, Hydrangea bendirei ( Ward) Knowl­ of Manchuria, of Oligocene age (FLORIN, ton, Liquidambar europaeum AI. Braun, Nyssa 1922); the genera are among the most crenata Chaney, Pinus knowltoni Chaney, commonly represented in the Arcto-Ter­ Pterocarya orer;oniana Chaney, Prunus tiary flora, such as AceI', Alnus, Betula, coveus Chaney, Rosa hilliae Lesquereux, Salix CercidiphyUum, Metasequoia, Platanus, Quer­ californica Lesquereux, and Sassafras bendi­ cus and Ulmus. Including records in other rei ( Knowlton) Brown. The total number Middle Tertiary floras of north-eastern of plant species now recognized in the Asia, twenty-six out of the total of thirty­ Bridge Creek flora is thirty-eight, and six genera making up the Bridge Creek flora there is little doubt that others will be are found at middle latitudes on both recognized in the course of studies now sides of the Pacific Basin. Kryshtofovich under way. has pointed out (1929, pp. 307-310) that The Arcto-Tertiary origin of this vegeta­ the older Tertiary forests of Siberia were tion has been extensively discussed (CHA­ made up largely of temperate types of NEY, 1947, p, 145). Five of the Bridge Creek hardwood deciduous trees, and has named species, Carpinus grandis, Cercidiphyllum the wide area which they occupied crenatum, Liquidambar europaeum, M eta­ in north-eastern Asia the Turgai province. sequoia occidentalis, Taxodium dubium, have His Turgayan flora is a part of what we been recorded from the Kenai flora of term the Arcto-Tertiary flora, which made Alaska, of Eocene age (HOLLICK, 1936), its way progressively southward following Twenty-four additional Bridge Creek genera the Eocene epoch, presumably in response are represented in this flora, in many cases to climatic and topographic changes. by closely related, probably identical species; When we come to consider the relation­ four additional species have generic re­ sh ips of the Bridge Creek flora to vegetation presentation elsewhere at high northern now living, it is apparent that the surviving latitudes. Only Cedrela merrilli (Chaney) elements of the Arcto-Tertiary flora have Brown appears to be certainly of southern continued their migration southward from 108 THE P!\.LAEOBOTA~IST

Oregon and Manchuria since the Oligocene obstacle to the westward flow of the Tertiary epoch. In North America the modern john Day River. The plant-bearing sedi­ descendants of most of the common members ments, which occur near the base of the of the Bridge Creek flora now reach their Mascall formation, were laid down in lake best development in the mixed deciduous basins and swamps which resulted from forest of the Cumberland Mountains, in impaired drainage. They are made up the south-eastern United States (BRAUN, largely of volcanic ash showing little evi­ 1942, p. 415). over 500 miles south of dence of transportation, and include abun­ the latitude of the john Day Basin (PL. dant diatoms. Overlying sands and conglo­ 3, FIG. 7). The only important excep­ merates give evidence of non-volcanic tions are Metasequoia occidentalis, Quercus deposition; these make up only a smalJ part consimilis and Cercidiphyllum crenatum, of the formation, and do not contain plant whose modern equivalents are found living fossils. Layers of lignitic shale are of together only in, and on the borders of, common occurrence in association with the the mixed deciduous forest of western plant-bearing beds, which are best developed Hup2h and eastern Szechuan, in central at several localities along the john Day China (CHENG, 1939, 1949). With the River east of Dayville. Closely related floras exception of Platanus, alJ of the common are found in the adjacent Blue Mountains Bridge Creek genera are represented by (OLIVER, 1934), and in the Stinking Water living species in this region, some 700 miles Basin to the southeast; the Latah flora south of the latitude in Manchuria where of eastern Washington (KNOWLTON, 1926), the Fushun flora is found. These modern the Payette of south-western Idaho (KNOWL­ forests of central China and the eastern TON, 1898), the Trout Creek of south­ United States, as illustrated on Plate 3, eastern Oregon ( MACGINITlE, 1933), and the are so similar to the Bridge Creek flora in Forty-nine Camp of north-western Nevada composition that they provide a sound ( LA MOTTE, 1936), all have many species in basis for reconstructing the physical setting common with the MascalJ flora, and appear in eastern Oregon during the closing days to be of essentialJy the same age. of the Oligocene epoch. In both regions The MascaJl column of Table I shows the they find their best development in valleys composition of this Miocene flora, and and on slopes; at the lower latitude of gives the numerical representation of its the China occurrence, the forest is not fifteen most abundant species, as based known to occur below an elevation of upon leaf counts of ten thousand specimens. 4,000 ft. ; the American forest is also welJ The total list of species is considerably developed at this altitude, and ranges larger than that of the Bridge Creek, and down to 1,000 ft. Climates of both regions there is little question that the Mascall are characterized by a wet growing season, forest was of a more varied type. Of the by annual rainfall totalling fifty inches sixty-eight recognized species, Carya bendi­ or more, and by average winter minima rei, Quercus pseudo-lyrata ;-md Taxodium only a few degrees below freezing. dubium make up nearly sixty-one per cent. With twelve other species, each of which COMPOSITION AND RELATIONS OF THE constitutes more than one per cent of MASCALL FLORA the total, they make up ninety-five per cent of the flora, and doubtless include The Mascall formation was laid down most or alJ of the trees which were dominant following the outpouring of basaltic lavas in the MascalJ forest (PL. 2). Like the in the j ohn Day Basin during Middle Bridge Creek, this flora appears to be largely Miocene time. Here it may represent the of northern origin. time equivalent of the upper part of the Columbia River Basalt, for in adjacent COMPARISON OF THE BRIDGE CREEK regions deposits containing a similar flora AND MASCALL FLORAS AND THEIR are inthbedded in this volcanic series. ENVIRONMENTS By the middle of the Miocene, the Cascade Range had been built up by flows and Of the nine genera most abundant at pyroclastics to a height which was altering Bridge Creek, Acer, Betula, Cercidiphyllum, the climate of eastern Oregon, and to a Metasequoia, Platanus, Quercus and Ulmus continuity which was already forming an are represented in the Mascall tlora. But CHANEY - CONIFER DOMINA~TS OF THE JOHN DAY BASIN 109 whereas Betula heteromorpha, combined in California, are strongly suggestive of with Alnus carpinoides, make up nearly well-drained slopes rather than of swampy half of the leaves and fruits of the Bridge ground. On the other hand, the living Creek flora, the birches and alders of the Taxodium dt'stichum has its best development Mascall, comprising four species, make in lowlands covered by streams during up little more than one per cent of the flood, or in swamps where water stands specimen count. The most abundant oak much or all of the year (PL. 4, FIG. 8) ; of the Bridge Creek, Quercus consimilis, in an extensive survey of the southern constituting six per cent of the total, is Atlantic coastal plain and lower Mississippi unrepresented in the Mascall, where four ri vel' drainage, I have never seen it growing species of lobed oaks, a type unknown naturally on a well-drained slope. The in North America before the Miocene reduction in number of trees of Metasequoia ( CHANEY, 1949, p. 194), make up nearly occidentalis from Upper Oligocene to Middle twenty per cent. Leaves of Acer, Platanus iVIiocene time, as judged by the greatly and Ulmus are all fairly common in both lowered representation of its leafy shoots floras, and some of the rarer genera of in the fossil record, and the still more the Bridge Creek, such as Celtis, Crataegus, marked increase of Taxodium dubium during Fagus, Hydrangea, Mahonia, Pinus, Populus, this interval, seem best interpreted as Ptelea and Salix, are also uncommon in the a response to the gradual blocking of drain­ Mascall. On the other hand, Cercidiphyllum age and the development of numerous crenatum, which is rare in the Mascall, lakes and swamps. Such a change in the comprises two per cent of the Bridge Creek; terrain would have been a natural result and Metasequoia occidentalis, only ninth of the major damming of Miocene rivers in abundance in the Mascall list, makes by the rising Cascade Range to the west, up over one-fourth of the specimen total and of minor blocking on a wide scale of of the older flora. The inverted ratios of streams small and large by lava flows, pyro­ Metasequoia occidentalis and T axodium dub­ clastic accumulations, and local warping. ium in the two floras indicate a significant If such changes in topography were change in the vegetation and environment taking place, we should expect to find of the John Day Basin from Oligocene to other evidence in the plant population. Miocene time, and will serve as the basis Comparison of the hardwood members of for our further discussion. the two floras fully substantiates the sugges­ As indicated above, Metasequoia glyptostro­ tion of progressively impaired drainage. boides is now confined to a limited area Most of the common associates of M. in central China; here it occupies well­ occidentalis in the Bridge Creek flora have drained slopes in deep valleys where there modern equivalents which are typically is heavy summer.rainfall and where winter trees of well-drained slopes, both in the temperatures are moderate. Too much United States and in China. With the emphasis cannot be placed upon details of exception of Platam/s, which in Eurasia the modern Metasequoia environment, since is now confined to the Near East, every this living tree has been logged off from common genus of the Bridge Creek all but the most inaccessible valleys. If flora, and many of those represented natural vegetation were preserved over a by only a few specimens, are now represented large surrounding area, it is probable by closely similar living species in the that we should find these redwoods of valleys of China where AIetasequoia has China living under more varied conditions, survived. The following lists show the and ranging northward at lower altitudes modern equivalents of the Bridge Creek than their present situation, between 4,000 species, or in some cases merely the generic and 4,500 ft. In any event we may be representatives, which have been observed confident from its deciduous habit that in immediate association with M. glyptostro­ M. occidentalis, the Tertiary ancestor of boides in the Shui-hsa-pa district of western this tree, also lived in a region of summer Hupeh (PL. 3, FIG. 6) ; the list of living trees rainfall. Whereas the living species may and shrubs is based upon my own ohserva­ be found under cultivation on the borders tions, supplemented by those of Drs. Cheng of rice paddies, its natural occurrence in Wan-Chun, and of Chu Kwei-ling, who car­ the valleys of western Hupeh, and the ried on field work in th is region during the behaviour of seedlings now under cuitivation summer of 1948 (Cm: & COOPER, 1950). 110 THE PALAEOBOTANIST

Oligocene Bridge Creek Flora Modern Forest at Shui-hsa-pa of Oregon

Metasequoia occidentalis (Newberry) Metasequoia glyptostroboides Chaney Hi.! & Cheng Pinus knozvltoni Chaney Pinus spp. Salix califor /lica Lesquereux Salix wilsonii Seemen Pterocarya oregoniana Chaney Pterocarya paliurus Batalin Betula heteromorpha Knowlton Betula luminifera Winkler Carpinus grandis Unger Carpinus fargesii Franchet Ostrya oregoniana Chaney Ostrya japonica Sargent Castanea orientalis Chaney Castanea !tenryi Rehder & Wilson Fagus pacifica Chaney Fagus 10llgipetiolata Seemen Quercus consimilis Newberry Quercus glalldulifera Blume Cellis obliquifolia Chaney Cellis labilis Schneider Ulmus speciosa Newberry Ul'mus mullinervis Cheng Cercidiphyllum crenatum (Unger) Cercidiphyllum ja ponicum Sl mcum Brown Rehder & Wilson Sassafras bet/direi (Knowlton) Sassafras tzumu Hemsley Brown Liquidnmbar europaem1'l Brown Liquidambar formosana Hance Hydrallgea bendirei (Ward) Hydrangea strigosa Rehder Knowlton Rosa !tilliae Lesquereux Rosa henryi Boulenger Prunus coveus Chaney Prulllis spp. A itallthus ovata Lesquereux Ailanthus vilmoriniana Dode A cer glabroides MacGinitie Acer spp. CoritUS ovalis Lesquereux CorllltS controversa Hemsley Nyssa crenata Ch:lI1cy Nyssa sinensis Oliver

There are several species of trees and rated by a span of some thirty million numerous evergreen shrubs now living in years. are closely related both in origin association with M. glyptostroboides, which and in physical requirements. have not been found in the fossil record, Comparison of the Mascall flora with the and we have no wish to indicate our belief forest now living on the swampy borders that the modern forest is an exact replica of the \Vabash river. in south-western of the Oligocene of Oregon. However, the Indiana, brings out an equally striking resemblance of the Bridge Creek flora to resemblance. The modern swamp cypress the vegetation in the mountains of western forest here is characterized by an abund­ Hupeh is so close. especially in the smaller ance of lobed oaks, hickory, sycamore, elm and more open ra vines where the variety and other trees which are common in the of trees is not great. that we have no hesita­ Mascall flora. as shown in the lists which tion in stating that the two forests. sepa- follow.

Miocene :Mascall Flora of Oregon :\lodern Forest in the Wabash Valley

T axodium dubium (Stern berg) Heer T axodium distichum Richard Smilax magna Chaney Smilax rotundifolia Linne Sal'ix hesperia (Knowlton) Condit Salix nigra Linne Populus heterophylloides Chaney & Populus heterophylla Linne Axelrod Carya bendirei (Lesquereux) Carya ovata Koch Chaney & Axelrod Betula thor Knowlton Betula /ligra Linne Ostrya oregonialla Chaney Ostrya virginiana Koch CHANEY - CONIFER DOMINANTS OF THE JOHN DAY BASI:\ 111

Quercus columbiana Chaney Quercus prinus Linne Quercus dayana Knowlton Querws nigra Linne Quercus merriami Knowlton Quercus palustn:s Du Roi Quercus prelobata Condit Quercus alba Linne Quercus pseudo-lyrata Lesquereux Quercus borealis Michaux Celtis dayana Chaney & Axelrod Celtis mississippiensis Bosc Ulmus paucidentata H. V. Smith Ulmus alata Michaux Ulmus specl:osa Newberry Ulmus americatta Linne Lindera hesperia Chaney & Axelrod Lindera benzoin (Linne) Blume Liquidambar pachyphyllum Knowlton Liquidambar stvraciflua Linne Platanus dl'ssecta Lesquereux Platanus occidentalis Linne Ptelea miocenica Berry Ptelea tyifoliata Linne Acei' bendirei Lesquereux AceI' saccharinmn Linne AceI' glabroides Brown Acei' rubrum Linne AceI' negund01des MacGinitie AceI' negundo Linne Nyssa hesperia Berry Nyssa sylvatica Marsh Diospyros andersonae Knowlton Diospyros virginiana Linne Fraxinus dayana Chaney & Axelrod Fraxinus quadrangu,fata Michaux

These lists include most of the common by the Mascall. This later forest, charac­ species of two forests separated in space terized by Taxodium dubium and other by nearly two thousand miles, and in time trees whose modern equivalents occupy by some twenty million years. Together the borders of swamps and shallow lakes, with the lists of the Bridge Creek flora and was widely distributed over the Columbia of the vegetation at Shui-hsa-pa. they Plateau during Middle Miocfl1e time. Conti­ present striking evidence of forest conti­ nued uplift of the Cascade Range brought nuity through geologic time. They also a reduction of rainfall and wider tem­ demonstrate that in the John Day Basin perature extremes to eastern Oregon. A the slope forest of the Oligocene, as re­ few representatives of Mascall hardwood presented in the fossil record by the Bridge genera have survived in the mountains Creek flora, gave way by Middle Miocene bordering the John Day Basin, but Taxodium time to a lowland forest with new dominants, and most of its lowland associates have as represen ted by the Mascall flora. Here been eliminated. changing conditions of drainage greatly Metasequoia occidentalis lingered on in reduced the abundance of Metasequoia oc­ small numbers as late as Middle Miocene cidentalis and its upland associates, and a time in North America, and it or an equi­ swamp forest characterized by Taxodium valent species is known to have continued dubium became widespread. down into the Pliocene in Japan. The scarcely distinguishable living species. M. CONCLUSION glyptostroboides. still lives in remote valleys The record of Tertiary rocks in the of central China where there is summer nort hem hemisphere indicates that M eta­ rainfall. The present regime of rainfall sequoia occidentalis and Taxodium dubium in western North America provides a ready have long been associated in mixed forests basis for explaining the disappearance of in which both coniferous and broad-leaved Metasequoia there, but its elimination from genera were largely deciduous. The Upper the Cumberland Mountains and elsewhere Oligocene forest of the John Day Basin, in the eastern United States, where so as indicated by the Bridge Creek flora, many of its hardwood associates have included M. occidentalis as a dominant. survived in a summer-wet climate, is more This flora was profoundly altered in Miocene difficult to explain. The cause of extinction time, when upland topography characterized here may lie in the unfavourable climatic by well-drained slopes was reduced to poorly extremes of the Pliocene and Pleistocene; drained plains by erosion and widespread preliminary success of current plantings of volcanic activity. Metasequoia and many Metasequoia seedlings in many parts of its of its upland associates became fewer in Tertiary range suggests that this tree may number or disappeared from Oregon, and now flourish in some areas from which it the Bridge Creek flora was supplanted was eliminated during post-Miocene time. 112 THE PALAEOBOT AN 1ST

Taxodium dubium lived on in western Basin, but not in the valley at Shui-hsa-pa ; North America into the Pliocene epoch, a forest of Mascall type is of recent age, and its failure to survive there to the present not Miocene, in the valley of the Wabash is doubtless also related to the shift from river. To judge with accuracy the age summer-wet to summer-dry climate. Its of sedimentary rocks from the plant fossils living equivalent, T. distichum, still occupies buried in them, we must not only determine topographically suitable environments in what kinds of trees and shrubs are re­ the eastern United States, in association presented, but we must know where other with modern equivalents of most of the similar forests have lived before and since. Mascall species. Sound concepts, both of time and space, of This comparison of the Tertiary forests palaeogeography as well as stratigraphy. are of Oregon with those of today indicates requisite to a solution of problems involving that during the ensuing millions of years forests which have migrated widely during since they first came down from the north, ages past. It is encouraging to know that there have been units of vegetation like these problems are now being studied on a them continuously in existence. Vegetation broad front, in Europe, North America and of the Bridge Creek type is an indicator Asia. wherever the Arcto-Tertiary flora has of Upper Oligocene age in the John Day left in the rocks a record of its wanderings.

REFERENCES BRAUN. E. Lucy ( 1942). Forests of the Cumber­ HEER, O. (11\55). Tertiare flora der Schweiz. 1. land Mountains. Ecological MOllographs. 12: Winterlhur. 413-447. HOLLICK. ARTHUR (1936). The Tertiary Floras CHANEY. RALPH \\'. ( 1924). Quantitative Studies of Alaska. U.S. Ceol. Surv. Prof. Paper 182: of the Bridge Creek Flora. Am. jour. Sci. 8: 1-175. 127-144. - Hu, HSEN-Hsu & WAN-CHUN CHENG (1948). Idem ( 1925). Comparative Stu-lY of the Bridge On the New Family Nlelasequoiaceae and on Creek Flora and the Moctern Redwood Forest. Melasequoia Glyploslroboides, a Living Species of Carnegie Irtsl. Wash. P"bl. 349: 1-22. the Genus Nlelasequoia Found in Szechuan and Idem (1927). Geology and PaJeontology of the Hupeh. Bull. Fan. Nlem. Insl. of Bioi. 1 (2): Crooked River Basin. with Special Reference to 153-16\. the Bridge Creek Flora. Ibid. 346: 45-138. KNOWLTON, F. H. (1898). The Fossil Plants of Idem ( 1938). An~ientForests of Oregon: A Study the Payette Formation. U.S. Ceol. Survey, 18th of Earth History in Western America. Ibid. Ann. Rept.: 721-736. 501: 631-648 - Idem ( 1926). Flora of the Latah Formation of Idem (1947). Tertiary Centers and Migration Spokane, Washington, and Coeur D'Alene, Routes. Ecol. i'vlo1lographs. 17 (2): 139-148. Idaho. U.S. Ceol. Surv. Prof. Paper 140: Idem (1948). The Bearing of the Living Nlela­ 17-82. sequoia on Problems of Tertiary Paleobotany. KRYSHTOFOVICH, A. N. (1929). Evolution of the Nat. Acad. Sci. 34 (II): 503-515. Tertiary Flora in Asia. New Pltylologisl. 28 Idem (1948). Pliocene Flora from the Rattlesnake (4): 303-312. Formation of Oregon. Bull. Ceol. Soc. Am. 59: LAMOTTE, ROBERT SMITH ( 1936) Middle Cenozoic 1367. Floras of \oVestern North America. Carn. l1'sl. Idem ( 1949). Evolutionary Trends in the Angio­ Wash. P"bl. 455: 29-148. sperms. Ce>lelics, Paleontology, alld ElIolulion. MACGINITIE, HARRY D. (1933). The Trout Creek 190-201. Flora of Southeastern Oregon. Ibid. 416: Idem (1951). Revision of Fossil Sequoia and 21-68. Taxodium in \-Vestern l\orth America Based MIKI, S. (1941). On the Change of Flora in on the Recent DiscovelY of Melasequoia. Trans. Eastern Asia since Tertiary Period (I). The Am. Pltil. Soc. 40: 169-263. Clay or Lignite Beds Flora in Japan with CHENG, W. C. ( 1939). Les Forets du Se-tchouan Special Reference to the Pin"s Irifolia Beds et du Si-kang oriental. Travaux du Laboraloire in Central Hondo. jap. jo"r. of Bol. 11: Foreslier de Toulouse. 1 (2): 1-212. 237-303 Idem ( 1949). Forest Communities. Unpublished OLIVER, ELIZABETH (1934). A Miocene Flora manuscript. from the Blue lV[ountains, Oregon. Carn. Inst. CHU, I{wEI-LING & \\'ILLlAM S. COOPER ( 1950). Wash. P"bl. 455; 1-27. An Ecological Reconnaissance in the Native STEBBINS, G. L. JR. (1948). The Chromosomes Home of Melasequoia glyploslroboides. Ecology. and Relationships of Melasequoia and Sequoia. 31 : 260-278. Sci. 108: 95-98. FLORIN, RUDOLF ( 1922). Zur alttertii\ren Flora WILLIAMS, HOWEL (1948). The Ancient Vol­ der siidlichen Mandschurei. Ceol. S-urv. China. canoes of Oregon. Ore. 51. Sysl. of Higher 1 (I): 1-47. Educ.,' 1-64. CHAXEY·- CO~JFERDOMINANTS OF THE JOH~ DAY BASIN 113

EXPLANATION OF PLATES

PLATE I /era, Castanea henryi, Cercidiphyllltm japonicum 1. Slab of volcanic shale from the Lower John sinicltm and Quercus glcindu/-i/era. The evergreen Day formation at the Twickenham locality, John conifer is Cumlinglwmia lanceolata. Day Basin, Oregon. Common members of the 7. Mixed decid uous forest of the eastern United Bridge Creek Rora shown are Jl1etasequoia occi­ States. Common trees are Betula papyri/era, dental-is, Betula heteromorpha and Cerc'idiphyllum Castanea dentala and Qu.ercus borealis. TIle ever- green conifer is rigida. • crenat,,,'}l (natural size). Pinus

PLATE 2 PLATE 4 Fossil leaves of the Mascall Rora (natural size). 2. Leafy shoots of swamp cypress, Tazodium 8. Forest of swamp cypress, Tazodium distichum, dubium ( upper left). and tupelo, Nyssa aql

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