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. GEOLOGY OF GREEN AND YAMPA RIVER CANYONS in the upper part of the'formatiou is considerably shattered, There is some lime- stone breccia in the lower part, This formation is quite porous, in part the result of partial dissolution of small fossils; such as minute cup corals, especially in some of the lower layers, The lack of arenaceous material suggests deep-water origin and uniform conditions of deposition during Madison time in this area, The Pennsylvanian sediments (Morgan formation), however, indicate more variable conditions. Between the Morgan and Madison formatious occur 90 feet of carbonaceous shale containing in the upper part a 4-fOOt quartz-sandstone layer bearing plant remains, Beneath these beds is a series of 60 feet of clear quartz-sandstones, white, yellowish, and red (hematitic) in color, Some of the sandstone is fine- grained and contains thin layers of carbonaceous material. Beneath these clastics occurs a 6-foot layer of limestone below which are 30 feet of reddish calcareous and angular conglomeratic sandstone, The writers have found lepidodendron and calamite plant remains at several localities in the sandstone beds, and it is hoped that some of these spec.imens may be identifiable and sufficiently diagnostic to determine whether these sediments belong to the Lower Pennsylvanian or to the Upper Mississippian period, One of the best Pennsylvanian sections in the Monument area occurs in Whirlpool Canyon (Green River), According to foraminiferal determinations by Lloyd G, Henbest,' of the United States Geological Survey, the Morgan forma- tiou of this region includes members of Des Moines, Atoka, and Morrow age, The lower limestones rest without apparent disconformity on the carbonaceous shale and sandstone beds described, although there does seem to be some suggestion of erosion locally among the clastics, The lower third of the Morgan formation con- sists predominantly of cherty limestone layers: The middle part includes fossilif- erous marls tone and limestone beds some of which contain varicolored cherts, The upper third of the formation consists of alternating limestone and fine- grained predominantly quartz-sandstone layers, the latter changing in color from red and terra' cotta to gray or buff near the top and greatly resembling the over- lying Weber sandstone as the contact is approached, Although the Madison is less fossiliferous than the Morgan, it seems possible that both formations might be a source of petroliferous deposits, The Weber sandstone is a fairly uniform fine- to medium-grained gray to buff friable sandstone, somewhat calcareous, thus susceptible itself to rapid erosion, It is moderately to strongly cross,bedded, in places suggesting wind deposition, Locally, the Weber formation becomes quartzitic, In many places the upper part contains petroliferous outcrops, Fossils are abundant in many of the formations. One of the most interesting of these groups is the Morrison dinosaurs of Upper Jurassic age, To them must be credited the establishing of Dinosaur National Monument, as it is this colorful series of Morrison flood-plain deposits in which occur the fossils that made the I Personal communication. .. I . 69I