isroTE. 



Generalized' section of sedimentary formations, with the local groupings adopted 

 hy the Geological Exploration of the Fortieth Parallel. 



In order to enable the reader to readily understand the local names of 

 the different series of strata used in the foregoing report, the following 

 table has been prepared, in which are grouped together all the divisions of 

 sedimentary rocks observed in the region explored, with the geological hori- 

 zons to which they belong. 



The character and relative thickness of each group are deduced from the 

 most characteristic developments which have been studied; and as these are 

 embraced in the wide region lying between the Great Plains and the Sierra 

 Nevada, it will be readily understood that this table does not represent 

 a section shown at any one point. The aggregate thickness given for each 

 of the larger subdivisions is estimated in general from the maximum develop- 

 ments of the individual groups. 



854 



