Page:The Journal of geology (IA journalofgeology21894univers).pdf/58

relations, namely, that during the Miocene the country was a series of plains and peneplains with low mountain ranges, or in other words, the country was but little above its baselevel of erosion. In no other position could such extensive plains have been formed by erosion.

The Ione formation being well stratified was evidently laid down in a body of water having a distribution at least as extensive as the formation itself. In the Sacramento valley, as far north as Marysville Buttes, the water of the bay was salt, as shown by the marine shells found at that point by Mr. Lindgren.^[1]

Upon the borders of this bay, at Ione, where the conditions were favorable for the accumulation of the vegetable matter to form lignite, the water was regarded as fresh or brackish. Farther northward only unios have been found, and the water in which the Ione formation originated was fresh. Beyond the Lassen Peak region in northern California the water was undoubtedly fresh, but whether one large lake or a series of lakes, or a water body connected directly with that of the Sacramento valley as an estuary from the sea, is a matter of doubt.

From the Great valley the sea swept across the region of the Coast Range, perhaps near the latitude of Sacramento, and extended northward over the area of the broad belt of sandstones upon the western slope to beyond Humboldt Bay. The borders of the land must have been low and swampy to make the conditions favorable for the accumulation and preservation of vegetable matter to form coal. The Sierra Nevada and Klamath Mountains themselves were low, with gentle slopes as compared with those of the present ranges, and the streams flowed down their flanks in broad, shallow valleys instead of in deep cañons as they do now.