NJTES DESCRIPTIVE OF SOME OEOLOGICAL SECTIONS OF THE 

 COUNTRY ABOUT THE HEADWATERS OF THE iMISSOURI AND 

 YELLOWSTONE RIVERS. 



Bv F. V. Haydkx. 



It is not intended that these notes shall emljrace a complete account 

 of the geology of Montana. They are simply designed to render the 

 beautiful pictorial sections which accompany them more intelligible to 

 the general reader. That these pictorial sections may reach the public 

 sooner, an edition of them is issued in this form. All the sections in this 

 paper represent the scenery along the immediate valleys of the Lower 

 Gallatin and Madison Kivers, with the exception of two, which are fine 

 illustrations of different portions of the Yellowstotic Valley. 



It is hardly possible for the pencil of the artist to delineate more 

 graphically or minutely the scenery of this interesting country than 

 these sections do. For the geologist very little descriptive text is 

 needed, and for the details of the geology he is referred to the Annual 

 Eeports of the Survey for 1871 and 1872. 



Should the Survey continue its operations from year to year by suit- 

 able grants of money from Congress, all the region, including the Yellow- 

 stone National Park, will be reexamined systematically and in detail; 

 what we have done up to this time must, therefore, be little more than 

 preliminary to the more thorough work that must come hereafter. 



I have always regarded the junction of the three forks of the Mis- 

 souri — the Gallatin, Madison, and Jefferson — as one of the most inter- 

 esting geographical points along the Missouri River, Here, within a 

 short distance of each other — a few hundred yards apart — these three 

 great streams unite in one, forming the Missouri Kiver. This junction 

 is most admirably shown in Plate I, upper sketch, which is really a pan- 

 oramic view of the valley with the surrounding hills. The view is taken 

 looking west from Gallatin Bluffs. At the right hand, at rr, the three 

 rivers have united into one channel, just at the upper end of a cafiou, or 

 gorge through Carboniferous limestones. 



In the bottom, and especially on the point between the Madison and 

 Jefferson Elvers, are remnants of Carboniferous limestone, with a few 

 characteristic fossils. These remnants are found at different points in 

 the immediate valleys of these streams, showing most clearly that the 

 broad space now occupied with the lake-deposits, between the Jefferson 

 a id Gallatin Eivers, was originally worn out of the sedimentary beds of 

 this locality. In other words, we obtain in this way a glimpse of the 

 tremendous magnitude of the erosive action in past times in this re- 

 gion. 



In the background are weathered hills, rising- from GOO to l.L'OO feet 

 above the valley, underlaid, for the most part, with the limestones of 

 Carboniferous age, inclining toward the north or northeast. Other for- 

 mations come in, farther and farther in the background, as the Juras- 

 Xo. 3 1 



