Lawson.] 



The Upper Kern Basin . 



325 



incisively, though not as deeply as the master stream. Toowa 

 Valley might be expected to be similarly trenched in the effort of 

 the streams which drain it to reach the lower base level estab- 

 lished by the master stream. The absence of such an incisive 

 trench traversing the floor of Toowa Valley constitutes an 

 apparent difference between it and Chagoopa Plateau. This 

 difference has been partially explained in the preceding discus- 

 sion of the geomorphic features of the valley. The succession 

 of meadows and alluvial flats, which constitute the bottom lands 

 of the valley, are there recognized as the result of aggradation, 

 due in large measure to the obstruction of the drainage by vol- 

 canic accumulations. These volcanic materials are themselves 

 found to have filled up a gorge which, in the lower stretch of 

 Volcano Creek, had been cut down nearly to the present level of 

 the Kern River in pre- volcanic time. It is not supposed that 

 this gorge had been cut very far back into Toowa Valley; but 

 the facts are sufficient to indicate that Volcano Creek had cut as 

 deeply below the ancient floor of Toowa Valley as other more 

 northerly tributaries of the Kern, Rock Creek, and the East 

 Fork of the Kern, for example, had cut below the floor of the 

 corresponding Chagoopa Plateau. 



The Little Kern Plateau. — We have still another plateau 

 which appears to fall into the High Valley system of the south- 

 ern Sierra Nevada. This is partly within the basin of the upper 

 Kern as defined in the earlier part of the paper and partly 

 extends beyond it. It was first met with in the southern end of 

 the basin, south of Trout Meadows, in the triangular piece of 

 country between the Kern and the Little Kern, beyond the end 

 of the Great Western Divide, and was followed up the west side 

 of the little Kern for some ten or fifteen miles as a broad, dis- 

 sected terrace. Its general altitude is estimated to be about 

 7,000 feet. Travelling south from Trout Meadows one crosses 

 an almost perfectly level floor, relieved only by low swales, to 

 the brink of the deep canon of the Kern near where it is joined 

 by the Little Kern. This level platform is veneered in places by 

 the remnants of a thin sheet of basaltic lava, which tends to 

 accentuate its flatness. The underlying granite appears fre- 

 quently, however, from beneath the lava and between the 



