More than nine-tenths of the Upper Cretaceous rocks in northeastern Wyoming are fine-grained shales, mudstones, and calcareous marls. A comparative study of the mineralogy, chemical and mechanical composition, density and porosity, fissility, and lamination of samples of these rocks discloses several relations that throw light on the geologic history and structural deformation of the region, and perhaps on its oil and gas possibilities.

Abstract: The identification of new collections of fossil plants from the Green River formation of middle Eocene age made it necessary to reexamine the megascopic types of the Green River flora. This study resulted in the reassignment of some species and the rejection of such species as were based on fragmentary, indefinable specimens. The recent collections yielded 22 new species. Exclusive of the microscopic forms of thallophytes and pollens, the flora now numbers 135 megascopic species that are considered to be recognizable and distinctive. The new elements found in the flora do not alter the previously expressed opinion that the megascopic Green River flora lived in a warm-temperate well-watered environment.

From introduction: The geologic record of the Tertiary period in the Green River Basin of southwestern Wyoming consists, in a broad way, of two quite different parts. The history of the first part, lasting through the Eocene epoch and perhaps on into the early Oligocene, was recorded in a thick series of sedimentary rocks of fluviatile and lacustrine origin. The history of the second part was recorded chiefly by successive stages of stream planation and stream trenching, but also in part by fluviatile sedimentation and, in certain localities, by glacial deposits. The first part of the record is virtually continuous, though its interpretation is by no means simple and obvious. The second part of the record is distinctly fragmentary, and the evidence the fragments provide is difficult to evaluate and to integrate.