Miocene Floras from Fingerrock Wash Southwestern Nevada By JACK A. WOLFE SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 454-N Description offossil plants from the southern Great Basin, with emphasis on their significance to phytogeography and jloristic evolution UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 UNITED STATES DEPARTMENT OF THE INTERIOR STEW ART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Systematics Continued Page Abstract_ ________________________________________ N1 Class Angiospermae_---_-------------___-------- N16 Introduction _______________________________________ 1 Subclass Monocotyledones. 16 Geologic occurrence-________________________________ 1 Order Glumiflorae___. 16 Floral composition and interpretation _________________ 3 Subclass Dicotyledones- _ _. 16 Fingerrock flora____-----_-_______-_-_-_________ 4 Order Salicales_ ______ 16 Systematic list of the Fingerrock flora.________ 4 Order Garryales. 19 Composition _______________________________ 5 Order Juglandales__. 20 Floristic relationships. ______________________ 5 Order Fagales________ 20 Order Urticales___--_. 22 Stewart Spring flora_____________________________ 7 Order Ranales___--__- 23 Systematic list of the Stewart Spring flora.____ 7 Order Rosales________ 23 Composition _______________________________ 7 Order Sapindales_ 28 Floristic relationships _ ______________________ 9 Order Rhamnales____. 30 Floral provinces in the Barstovian________________ 10 Order Myrtiflorae__. 30 Biostratigraphy_ ________________________________ 12 Order Ericales__------ 31 Systematics- _______________________________________ 13 Incertae sedis ________ 31 Class Gymnospermae____________________________ 14 References cited._________________ 32 Order Coniferales___________________________ 14 Index __________-__________-----. 33 ILLUSTRATIONS [Plates 1-12 follow Index] PLATES 1-5. Fingerrock flora. 6-12. Stewart Spring flora. FIGUEE 1. Index map of the Fingerrock Wash area._____-_________________________________----_-_--------_--- N2 2. Composite stratigraphic section of part of the Tertiary rocks on the west flank of Cedar Mountains_______ 3 3. Distribution map of Picea breweriana, Quercus chrysolepsis, and Chamaecyparis nootkatensis_____________ 9 4. Sketch map of the Great Basin showing location of some Neogene floras________________-_--_--_-_---_- 11 5. Abies sp--__--__-_______-__________________________________________________-----__---__-------- 14 6. Cupressaceae___-________________-_______________________________________-_-_--__-_-_-__-------- 16 7-12. Marginal venation of 7. Populus.- ________________________________________________________________________________ 17 8. Salix- ___________________________________________________________________________________ 19 9. Garrya.-- _______________________________________________________-___-_- 20 10. Betula-.. _____________________________________________________-___---_- 21 11. Amelanchier ______________________________________________________________________________ 24 12. Cercocarpus-- ______________________________________________________--__-_-_--_-_--_------- 25 13. Distribution map of fossil Cercocarpus- _________________________-_-___-____-__-_---_--------------- 26 14. Marginal venation of Holodiscus----,------------------------------------------------------------- 26 15. Venation of Lyonothamnus- _______________________________________________---_-----_----_-------- 27 16. Distribution map of fossil Lyono.fta?ranMS___________________________________----_-_----------------- 27 17-20. Marginal venation of 17. Peraphyllum. _____________________________________________-_______----_---_-_---_--_------ 27 18. Eoso_______________._____________________________________________________________________ 28 19. Schinus-----. __________________________________________________-_--_-_--------- 29 20. Astronium. _______________________________________________________----_------------------- 29 21. Apical venation of I-7aea0rms_____________________________________________------------------------ 30 22. Marginal venation of Arctostaphylos--.-.---------------------------------------------------------- 31 TABLES Page TABLE 1. Numerical abundance of Fingerrock fossils____________________-_-__________--_--------------------- N5 2. Numerical abundance of Stewart Spring fossils________________________-__-_---_-------------------- 7 3. Comparison of relative abundance of spruce, live oak, and cedar in the Nevada Barstovian and Clarendonian floras_ _-__-___________________________________________________________-------------_--------- 8 4. Correlation of some Neogene floras of the Great Basin_____________________--------_---------------- 13 ni SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY MIOCENE FLORAS FROM FINGERROGK WASH, SOUTHWESTERN NEVADA By JACK A. WOLFE ABSTRACT brate fossils, and the plant localities can be related Two floras of Miocene age, the Fingerrock and Stewart stratigraphically to the mammalian geochronology. Spring, are found in a stratigraphic section that also contains One locality occurs several hundred feet lower than an fossil mammals. The Fingerrock flora occurs in beds below early Barstovian fauna and is therefore considered to the Stewart Spring local fauna of transitional Hemingfordian- Barstovian (middle-late Miocene) age, and the Stewart Spring be Hemingfordian (middle Miocene) at the youngest. flora occurs above that fauna but below the Cedar Mountain The other localities occur in paper shales between the local fauna of Cerrotejonian (earliest Pliocene) age. beds containing early Barstovian and Clarendonian The late Hemingfordian Fingerrock flora was dominated by mammals, and thus this flora can be considered of mid­ the live oak, Quercus chrysolepis, but most of the flora is com­ posed of species found in contemporaneous floras of the dle or late Barstovian age. Columbia Plateau. These species include lobed Quercus, Carya, The paper shales mentioned above are not only no­ Ulmus, Zelkova, Platamis, and Acer. The lack here of certain table for the abundant and well-preserved leaves, seeds, other species found in this association to the north indicates and flowers but also for numerous fossils of insects and that the Fingerrock flora lived in a drier climate than prevailed fishes. Exhaustive collecting in the future will prob­ at the same time on the Columbia Plateau. Nevertheless the ably bring these paper shales the same prominence as Fingerrock flora was a warm-temperate mesophytic flora. Twenty-four species are described from the Fingerrock flora, the famed paper shales near Florissant, Colo. none of which are new. The paper-shale locality was first found by Mr. S. D. The early, or more probably middle, Barstovian Stewart Webb of the University of California (Berkeley). Spring flora is, besides the expected lacustrine element, dom­ Other vertebrate paleontologists have assisted in the inated by Quercus chrysolepis, Picea breweriana, and Chamae- collection of the fossil plants and in the discussion of cyparis nootkatensis. This assemblage is typically found only in western Nevada and is further restricted to floras of Bar­ mutual problems, and I particularly wish to thank stovian and Clarendonian age. Most of the species in the Prof. D. E. Savage and Mr. J. K. Mawby, both of the Stewart Spring flora appear to be descended from northern University of California (Berkeley). Dr. H. D. Mac- mesophytic forms, although the flora has a subhumid aspect Ginitie has contributed in the discussion of paleo- different from the northern floras. Only a small element in the Stewart Spring flora may contain species of southern origin. botanical problems. Several phylads in the Stewart Spring flora are now found on GEOLOGIC OCCURRENCE the margins of and in the Great Basin. The Stewart Spring flora contains 42 described species, 9 of which are new. The fossil plants occur in a sequence of volcanic rocks lying in a north-south basin on the west flank of the INTRODUCTION Cedar Mountains (fig. 1). The lower part of the se­ The Miocene floras of the southern Great Basin are quence is composed primarily of basaltic and rhyolitic of interest because it was in this region during the flows with interbeds of tuffaceous sediments. There is Miocene epoch that the subhumid flora first became no evidence in the lower part of widespread lacustrine dominant (Axelrod, 1958). Axelrod (1956, 1958) de­ conditions, and the sediments appear to have been de­ scribed and discussed some of the "Mio-Pliocene" floras posited in rivers and ponds. of the southern Great Basin. With the exception of the The Fingerrock flora (USGS paleobotancial loc. middle Miocene Tehachapi flora (Axelrod, 1939), how­ 9882) occurs in the lower part of this section, in a buff- ever, knowledge of middle and early late Miocene floras colored water laid tuff that crops out for a lateral extent from this area is singularly lacking. of about 150 yards. On weathering the tuff is white. In 1960, vertebrate paleontologists from the Univer­ To the south, the sedimentary rocks dip under a series sity of California discovered several new plant lo­ of rhyolitic flows. About one-quarter of a mile to the calities in the Stewart Valley of southwestern Nevada. south of locality 9882, tuffaceous rocks containing mam­ This region is already well known for numerous verte­ mals (the Stewart Spring local fauna)