Geol.— Vol. II.] ANDERSON— CRETACEOUS DEPOSITS. 21 



sandstone, with basal conglomerates, all of marine origin, 

 and containing several fossil species common in the Upper 

 Cretaceous of California. Besides the molluscan remains, 

 these deposits contain several species of saurians and certain 

 plants, some of which have been described by Steinmann 

 (1895) and his associates. 



6. Correlation. 



But little can be done at correlating these widely separated 

 deposits upon purely stratigraphical resemblances. In no 

 one section is there a series that can find its exact parallel 

 in any other, much less in all the others. It is to be 

 noticed throughout, however, that the cycle of sedimentation 

 in these deposits is the reverse of the normal order. Shales 

 invariably are more abundant in the lower part of the sec- 

 tions, sandstones increase as one ascends the series, and 

 conglomerates are more common in the upper portions. 

 This is sometimes so, even where there is only a part of the 

 entire series present, as in the vicinity of Medford and 

 Ashland, in Rogue River Valley, Oregon. Yet this is not 

 always so; at Horsetown and at Ono, Shasta County, the 

 local base of the Cretaceous contains heavy beds of con- 

 glomerate. But little reliance can be placed in these con- 

 glomerates, however; for as Diller has stated, they are 

 often of only local extent, and may merely show the position 

 of some stream in mid-Cretaceous time. Their irregularity 

 nevertheless affords some interesting suggestions. 



The regional subsidence and the deposition of these beds 

 could not have been quite so continuous as has been imag- 

 ined, thouofh the disturbances have been more or less local; 

 still, there are some broad uniformities- noticeable in the 

 widely distributed deposits. Tawny or grayish sandstones 

 and pebbly conglomerates characterize the Chico and Upper 

 Horsetown ; while dark or yellowish clay shales are more 

 common in the Knoxville portion of the series. If the 



(3) October 28, 1902. 



