DRAINAGE OF THE LIGNITE AREA

Four-fifths of the lignite area lies within the drainage basin of the Missouri river. The Mouse river drains the remainder, with the exception of a very small section in the center of the state, near Harvey, which contributes to the waters of the James. The practically undrained region in the morainic tracts of the Coteau du Missouri lies for the most part within the area that naturally sends its waters to the Missouri. and ultimately most of it will be drained in this direction, though the other streams just mentioned would doubtless profit in a small measure by this territory.

The Missouri crosses the lignite area nearly diagonally and the sharp cut banks so common along its course reveal vast quantities of this valuable fuel. From the east and north the river here receives no large tributaries, the most noteworthy being White Earth Creek in western Ward county, and Sandy Creek, which unites with it at Williston. Beaver Creek in Emmons county is reaching back into the morainic area, and is already a stream of some size. In addition to these are a multitude of smaller creeks from fifteen to twenty miles long, which have rather mature valleys in the older drift and are now cutting headward into the Wisconsin drift with great vigor.

On the south and west the tributaries of the Missouri are much larger, doubtless because of the fact that the glacial drift here but slightly affected topographic conditions. The Little Missouri is a stream of considerable size. Entering the state at the southwest corner, it flows north for one hundred and twentyfive miles, then turns to the east and after a course of seventyfive miles unites with the parent stream. During spring and late. fall it discharges a very large amount of water, while during the summer its volume is variable, at times dwindling to a stream of small dimensions.

The same variations are characteristic of the Cannon Ball, and Knife and Heart rivers. The innumerable small tributaries of these streams, not indicated on any published map, ramify the region and readily draw off the down pour of rain storms which even in summer are often severe.

The lignite area abounds in living springs, most of which issue from the lignite itself. Unaided by artificial conditions the larger ones will often fill a four inch pipe with a strong stream. In the subsequent reports the locations of many of these springs

will be noted. On account of these springs many of the creeks are perennial for a short distance from the parent stream. During the summer, the evaporation due to the heat and wind materially affects the amount of the water flowing in the creek channels and strong springs result only in forming a series of pools, separated by sand or gravel barriers through which the water seeps to a lower level.

The Yellowstone river unites with the Missouri so close to the western boundary that it is hardly a factor in the drainage of the state. Its broad valley, combined with its large volume of water fender attractive the possibilities of irrigation along its course in this state, as well as in Montana.

In Wlliams and Billings counties a few lakes are indicated on the map and some shallow ponds actually exist. Billings county is free from drift and Williams county lies outside of the area of the Wisconsin drift, so that this indication of incomplete drainage can not be ascribed to glacial agencies. Where actually seen these ponds could be accounted for in one of two ways. A tributary stream at times is a more active erosive agent than the parent stream and deposits debris at their point of meeting sufficient to form a barrier behind which a considerable quantity of water may be held. In the region under consideration barriers in stream channels are more commonly formed by the slipping of the Cretaceous clays. This tendency of the clay to slide in large masses is noticeable throughout the lignite area, and shows itself commonly in crescent shaped depressions on the hillsides.

The drainage of Ward county is given in the report which follows.

STRATIGRAPHY

GENERAL RELATIONSHIPS OF STRATA.

The restriction of the term "lignite area" to the region in which workable seams of lignite may be found greatly simplifies the stratigraphic series, and practically reduces this chapter to a consideration of the Laramie and of the drift. The thin seams of lignite farther east, along the Cheyenne river, regarded by Upham as possibly belonging to the Benton* are by this definition excluded from the discussion. The age and nature of the form. ations are shown in the following table:

*U. S. Geological Survey, Monograph XXV, page 92.

only.

The table just given includes the surface formations Deep well borings would bring to light under these, the lower Cretaceous and other members of older series. It is the purpose of the present report to consider only exposed formations, the discussion of underlying series being better left for a subsequent report when the stratigraphy of the state as a whole can be considered.

THE FOX HILLS SANDSTONE.

Todd, in Bulletin 144 of the United States Geological Survey has referred certain sandstone in southern Burleigh county and northern Emmons county to this formation. He says: "The presence of Fox Hills sandstone is shown by the capping of a butte encircled by Long Lake, just outside of the moraine, also by the conspicuous outcroppings along Sand creek, a steam flowing into the lake from the south, and about the borders of the tableland southwest. The same formation is similarly developed along Long Lake creek, which, rising near Long Lake, flows southwest in a large valley to the Missouri river near old Fort Rice." A sandstone which he regards as Fox Hills, is found ten or fifteen feet below the surface north of Steele.*

*Bulletin 144, United States Geological Survey, page 55.