Geological Survey Bulletin 204 Fossil Flora of the John Day Basin, Oregon

(1) The John Day Basin lies between the north and south ranges of the Blue Mountains, in north-central Oregon. It covers an area of approximately 10,000 square miles and is drained by John Day River and its tributaries. It has been the scene of great volcanic activity, its rock masses being made up of numerous volcanic flows, with alternations of ashes, tufas, sands, and gravels.

(2) No detailed geological study has been made of the region, but contributions to this subject have been made by Le Conte, Condon, Marsh, Cope, Wortman, Matthew, and Merriam, the most important and comprehensive being by the latter author.

(3) Its fossil riches, in the shape of mammalian teeth, were first brought to scientific attention in 1861. Since that time an extensive vertebrate fauna has been described by Leidy, Cope, Marsh, Wortman, Merriam, and others.

(4) The first fossil plants were found at Bridge Creek in 1862, by Prof. Thomas Condon. Since that date collections of plants have been made by Condon, Voy, Bendire, Merriam, Osmont, and Knowlton. The plants have been studied and described by Newberry, Lesquereux, and Knowlton.

(5) The fossil flora of the John Day Basin, as set forth in the present paper, comprises 150 forms, distributed among 37 natural families and the anomalous group of Phyllites. Of the 150 forms enumerated, 24 have not been named specifically, and 44 species and 1 variety are described as new to science. The previously known species number 81.

(6) The known fossil floras of the John Day Basin are all of Tertiary age. The oldest, represented by the localities of Cherry Creek, Currant Creek, and 3 miles above Clarnos Ferry, is referred to the Lower Eocene. It is in the lower part of Merriam's Clarno formation. The next younger in age, exposed at Bridge Creek, 1-1/2 miles east of Clarnos Ferry, one-half mile northeast of Fossil, and Officer's ranch in the Butler Basin, occupies the upper part of the Clarno formation and is Upper Eocene in age. The youngest plant-bearing beds of the region, found at Van Horn's ranch and vicinity, are in the basal portion of the Mascall formation. The age is regarded as Upper Miocene.

(7) From the facts adduced in this bulletin it is concluded that the conditions which prevailed in the John Day Basin during Tertiary times extended also into central Washington, northwestern Idaho, and western Oregon.