Chapter Title: Wasatchian Through Duchesnean Biochronology Chapter Author(s): Peter Robinson, Gregg F. Gunnell, Stephen L. Walsh, William C. Clyde, John E. Storer, Richard K. Stucky, David J. Froehlich, Ismael Ferrusquia-Villafranca and Malcolm C. McKenna Book Title: Late Cretaceous and Cenozoic Mammals of North America Book Subtitle: Biostratigraphy and Geochronology Book Editor(s): Michael O. Woodburne Published by: Columbia University Press. (2004) Stable URL: http://www.jstor.org/stable/10.7312/wood13040.10 JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://about.jstor.org/terms Columbia University Press is collaborating with JSTOR to digitize, preserve and extend access to Late Cretaceous and Cenozoic Mammals of North America This content downloaded from 132.177.228.65 on Tue, 20 Sep 2016 14:39:00 UTC All use subject to http://about.jstor.org/terms Woodburne_04 2/17/04 1:34 PM Page 106 4 Wasatchian Through Duchesnean Biochronology Peter Robinson, Gregg F. Gunnell, Stephen L. Walsh, William C. Clyde, John E. Storer, Richard K. Stucky, David J. Froehlich, Ismael Ferrusquia-Villafranca, and Malcolm C. McKenna HE PREVIOUS EDITION of this chapter (Krishtalka et which is refinement of Wasatchian through Duchesnean T al. 1987) assembled much information about the areal biochronology. This biochronologic framework will distribution and biochronology of the continental rocks remain unaffected by the ultimate placement of the and faunas representing the Wasatchian through Du- Paleocene–Eocene boundary, which may be placed at the chesnean North American land mammal ages (NAL- Dababiya section in Egypt (Aubry 2001). It is clear that MAs). That edition detailed the history of the classifica- most of the Wasatchian and all of the Bridgerian through tion of terrestrial rocks, particularly of western North Duchesnean will be recognized as representing the America, and included some information on radioiso- Eocene and contingent on the final position of the Global topic and paleomagnetic determinations. This revision Stratotype Section and Point (GSSP), all of the concentrates on the inclusion of new data and includes Wasatchian may ultimately be included in the Eocene. expanded information concerning Mexico and Canada. The Chadronian LMA is considered latest Eocene We introduce new information about radioisotopic ages (Swisher and Prothero 1990) but is addressed in the fol- and paleomagnetic correlations. Wherever possible, we lowing chapter. include data from unpublished sources and do not repeat The prior edition of this chapter pointed out that the data already cited in detail. The bibliography is as inclu- terminology for the NALMA discussed was based on for- sive as possible. We stress field information. mational names and that the resulting confusion of the Recently the definition of the Paleocene–Eocene differences between what is contained in a rock unit and boundary has been reviewed and is still under discussion what is contained in a temporal unit with essentially the (Aubry 1996, 1998, 2000; Berggren and Aubry 1998; same name is regrettable, even though the temporal Gingerich 1989, 2000; Gunnell 1998b; Koch et al. 1992). A boundaries are flexible (Wilson 1975). This situation has recommendation has been put forward to locate the lower not changed significantly for the LMAs in the interven- boundary of the Eocene at the negative carbon isotope ing years, although there has been much more precision excursion (CIE) in chron C24r (Koch et al. 1992; in the methods of collecting and recording data, and sub- Gingerich 2001), at the beginning of the Wasatchian land divisional terminology has helped. That the inconsisten- mammal age (LMA) in North America. The base of the cies of the Wood committee (Wood et al. 1941) remain is Wasatchian is marked by a major vertebrate faunal im- obvious, but they are recognized as such. Many assem- migration event including the widespread dispersal in the blages have been studied since the publication of the Northern Hemisphere of the orders Artiodactyla, Peris- Wood committee report. Faunal sequences in several of sodactyla, and Primates, as well as hyaenodontid Cre- these show that the age boundaries are not, need not be, odonta. The ultimate location of the Paleocene–Eocene and probably should not be synchronous with lithostrati- boundary is in some sense irrelevant to the goals of this graphic boundaries. For example, in several subunits of chapter (but see “Geochronology” later in this chapter), the Greater Green River Basin, Bridgerian mammals have This content downloaded from 132.177.228.65 on Tue, 20 Sep 2016 14:39:00 UTC All use subject to http://about.jstor.org/terms Woodburne_04 2/17/04 1:34 PM Page 107 Wasatchian Through Duchesnean Biochronology 107 been recovered from rocks referred to the upper part of River Basin (Carter, Wyoming, located in the Bridger Basin the Cathedral Bluffs Tongue of the Wasatch Formation, of authors) and the southern part of the Fossil Basin and Uintan mammals have been recovered from beds (Wasatch Station). Cope (1877, 1882) extended the usage high in the Bridger Formation (Evanoff et al. 1994). Most of Wasatch beds to the San Juan Basin in New Mexico and of the lower part of the Duchesne River Formation is Uin- the Bighorn Basin in northwestern Wyoming, identifying tan in age, whereas some of the lower part and the upper the rocks as the Coryphodon zone. Hayden (1878) similarly part are Duchesnean (Gazin 1955; Clark et al. 1967; referred sedimentary rocks in the Wind River Basin of cen- Tedford 1970). Table 4.1 lists the more significant tral Wyoming to the Wasatch Formation. Wasatchian through Duchesnean fossil mammal locali- The informal name Gray Bull beds was proposed ties relevant to this chapter. (Granger 1914) for the lower part of the Bighorn Basin se- The four NALMAs discussed here are based on mam- quence. Granger (1914) extended the Lost Cabin beds (or malian fossil assemblages (figure 4.1) from two Rocky Lambdotherium level) into the Bighorn Basin and referred Mountain basins: the western Green River Basin rocks between the Lambdotherium-bearing deposits and (Wasatchian and Bridgerian) and the Uinta Basin (Uin- the Gray Bull beds to the Lysite beds. The Lysite and Lost tan and Duchesnean). This terminology has been corre- Cabin beds had initially been recognized as distinct units lated outward from these two basins and is used through- by Granger (1910), and the two names were proposed as out North America. The term Wasatchian is derived from formations by Sinclair and Granger (1911). A geologically the Wasatch Formation and its faunas in the Greater older stratum, the Sand Coulee beds, was recognized in Green River and Fossil basins; all of the Wasatchian sub- the Bighorn Basin by Granger (1914). ages are actually derived from the faunal content of the Lithostratigraphic terminology has been standardized Willwood and Wind River Formations (Sandcouleean, in Wyoming basins. Wasatchian rocks of the Wind River Graybullian, Lysitean, and Lostcabinian). The term Basin are represented in part by the Wind River Forma- Bridgerian is taken from the Bridger Formation of the tion and include the Lysite and Lostcabin members. Greater Green River Basin, and two of its accepted sub- Temporally, the Wind River Formation spans the late age names are based on lithologic members of that for- Wasatchian to early Bridgerian time, with three faunal mation, a situation that has to change, as will be shown levels: Lysitean, Lostcabinian, and Gardnerbuttean. The later in this chapter. “Big Horn Wasatch” was formalized by Van Houten Gingerich (1989, 2001) and his coworkers have devel- (1944) as the Willwood Formation. The Willwood For- oped a terminology for the subdivision of the Wasatchian mation is conformable in most places on rocks variously (biochrons Wa0 to Wa7) that has been modified for other referred to the Fort Union Formation and is subdivided NALMAs, such as biochrons Br0–Br3 (Gunnell 1998a; lithologically, in the southern part of the basin, into the Gunnell and Yarborough 2000). This terminology will be Elk Creek and Sand Creek facies (Bown 1979b). The term used and expanded here to include a revised subdivision Wasatch Formation unfortunately is still used for the of the Uintan; the Duchesnean is not subdivided here. upper Paleocene and lower Eocene sediments of the Pow- der River Basin, although this basin is physically sepa- rated from the Greater Green River Basin by both the Wind River and Hanna basins. HISTORY OF TERMINOLOGY Veatch (1907) subdivided Hayden’s Wasatch into three formations: Almy at the base, Fowkes disconformably We present here an abridged version of historical termi- overlying it, and Knight at the top. The type localities of nology. See Krishtalka et al. (1987) and references therein these formations are all in the Fossil Basin. In 1960, the for more detailed accounts. U.S. Geological Survey standardized usage of Wasatch Formation across the entire Green River Basin area, in- cluding the Washakie Basin and Great Divide Basin (sensu WASATCH FORMATION Love 1961; now all included in the Greater Green River AND WASATCHIAN LMA Basin). Oriel