THE LOMBARD OVERTHRUST AND RELATED FEATURES 281 



fossils from certain of the members. A detailed account of the 

 formation and a description of some of the fauna is in process of 

 publication elsewhere, 1 so that only the more important points 

 will be mentioned here. 



In all of the region included in Fig. 1 the Three Forks formation 

 shows seven fairly distinct lithologic divisions. These members 

 are well shown in the following section of the formation made 

 northeast of Logan near the Gallatin River. 



Base of Gray Madison Limestons 



i. Yellow arenaceous limestone 30 feet 



2. Pale-yellow arenaceous shale 30 



3. Purple fissile shale 0.5 



4. Dark bluish-gray nodular limestone 9.5 



5. Fissile green shale 47 



f Yellow crystalline limestone 15 



\ Gray limestone 12 



7. Yellow and orange shales 78 



Top of the Jefferson limestone. Total 222 feet 



Another section farther north along the Missouri River at 

 Rekap Station (Fig. 7), shows the variation in thickness of the 

 different members. 



1 and 2. Yellow sandy limestone and shale . 74 feet 



3. Black coaly shale 6 



4. Nodular gray limestone 7 



5. Fissile green shale 



and 1 120 



6. Gray and yellow limestone 



7. Pebbly yellow and reddish limestones and 



shales 80 



Total 287 feet 



It will be noted from these two sections that the members con- 

 sist of limestones as well as shales, so that the term "Three Forks 

 formation" is preferable to Dr. Peale's name "Three Forks shales." 



In the region north of Three Forks and west of the Missouri 

 River there are numerous good exposures of the Three Forks 



1 Annals Carnegie Museum, Pittsburgh. 



