This paper is a preliminary report on the first of a series of studies which will attempt to establish recognizable foraminiferal zones in the Cretaceous sequence of eastern Colorado. Because previous reports on the Niobrara and Benton horizons of Nebraska, Kansas, and Wyoming have shown abundant faunas, these horizons in the foothills of the Front Range of northern Colorado were chosen as the most promising for this investigation. Progress thus far reveals a fauna of upwards of thirty species from the Niobrara. Indications are that this fauna is most prolific in the lower 300 to 400 feet of the formation and that this zone should be rather easily recognizable in well cuttings. The upper member of the Benton, which is a sandstone of variable thickness, seems to be entirel barren of fossils. About 125 to 200 feet below this is a zone of limy shale which yields a fair fauna of Foraminifera. This fauna is apparently very similar to, but less abundant than, that of the overlying Niobrara, and can not be readily separated from the latter in northern Colorado.

It is planned to extend this study of the Benton and Niobrara south to beyond Trinidad, Colorado, and also eastward along the Arkansas River to the Kansas boundary. Scattered samples from Benton outcrops north and east of Trinidad indicate a more abundant fauna of Benton age will be found; also that the barren zone of the top of that formation in northern Colorado is not present to the south.

End_of_Article - Last_Page 940------------