830 INDEX TO THE STRATIGEAPHY OF NORTH AMERICA. 



The time of the beginning of the John Day deposition appears to correspond with that of 

 the close of the Leptauchenia zone in the South Dakota region, namely, the upper Oligocene. 

 ********* 



The volcanic materials of the John Day were chiefly wind blown, as described by Merriam;" 

 there is little evidence of fluviatile conditions. The MoUusca are terrestrial or air breathing, 

 with the exception of one locaHty which contains fluviatile MoUusca. The Testudinata, genus 

 Stylemys, are of the Testudo or terrestrial type; no fluviatile types have been recorded. The 

 so-called beavers (Castoridse) are not the true river-livuig beavers (Peterson) . 



The known fauna of the John Day formation as a whole is chiefly of open-forest and 

 savanna-hving type. We note the entire disappearance of the ancient fauna, Creodonta- 

 Hysenodontidse, and do not observe the introduction or invasion from Eurasia of any new 

 families of mammals. The major part of the John Day fauna is of upper Ohgocene age, but in 

 its latest phases it is perhaps transitional to lower Miocene. The fauna is thus broadly transi- 

 tional between that of the White River group and the Arikaree formation. 



*** * * * *** 



The lower John Day fauna is so Httle known that no deductions can be made from it, 

 except that it appears to be closely related to that of the middle John Day. The faunistic 

 comparison of the John Day formation therefore begins with the middle John Day, which is 

 highly f ossflif erous and sKghtly more advanced than that of the upper portion of the Brule clay 

 and "Protoceras sandstones." 



*** * * * *** 



The conclusion is that the middle John Day deposition partly overlaps and is partly sequent 

 to the deposition of the upper part of the Brule clay and the ' 'Protoceras sandstones." 

 *** * * * *** 



The upper part of the John Day formation, or Promerycochoerus zone, of the Mountain 

 region of Oregon, as well as the Gering and Monroe Creek formation of Hatcher, the Gering or 

 lower Arikaree of Darton, the Rosebud of Matthew, all in the plains region of South Dakota, 

 may be regarded as covering the transition between the Oligocene and Miocene epochs, as these 

 divisions are employed in France. They resemble chiefly the upper Oligocene of France. 

 *** * * * *** 



It is concluded that the upper part of the John Day, for the present, may be somewhat 

 arbitrarily separated as the American upper Oligocene, while the partly contemporaneous and 

 partly sequent plains formations may be termed lower Miocene. 



The Columbia River basalt (Miocene) is the dominant formation of the Colum- 

 bia Plateau. Overlying it in Washington are the strata described by Russell "'^'^^^ 

 as lake beds and assigned by him to the John Day formation, but apparently of 

 later age. Russell states in his later report : **' 



In my report of a reconnaissance in central Washington certain lacustral deposits are 

 described which rest on the surface of the latest extensive lava flow of the Columbia system. 

 This series of lake sediments consists principally of stratified clays, with thick strata of white 

 volcanic dust, and in certain localities contains beds of coarse conglomerate. It is termed the 

 John Day system, for the reason that it is thought to be an extension of a similar formation 

 which occurs in John Day Valley, Oregon. The connection between these two areas has not 

 been actually traced, however, and the correlation just suggested must be considered as 

 provisional. 



Beds of Hght-colored clay and of white volcanic dust, which have been referred to the John 

 Day system, occur at the White Bluffs of the Columbia, 30 miles above Pasco, and are also well 

 exposed in Naches Valley and near EUensburg, in Yakima County. At these localities the 

 impressions of the leaves of a large variety of plants and the bones of extinct animals have been 

 obtained. The plant remains indicate that the shores of the ancient lake into which they were 



" A contribution to the geology of the John Day Basin: Bull. Dept. Geology Univ. California, vol. 2, 1901, pp. 

 269-314. 



