80 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH SER. 
nants of terraces, though they can hardly be called stream- 
terraces. 
The highest river-terrace proper is at an elevation of nearly 
850 feet above the sea, and on the south side of the river 
forms a broad mesa with an undulating surface. This may 
mark the level of a late Pliocene or Pleistocene delta, which 
will be referred to later. 
The various terraces here described probably represent 
former flood-plains of the river, developed during the gradual 
elevation of the region. River gravels are strewn abundantly 
over all of these terraces, and even river boulders occur on 
some of the ridges 700 or 800 feet above the floor of the 
valley. These topographic features are fairly well shown on 
the Bakersfield special topographic sheet of the U. S. Geolog- 
ical Survey. 
BASE-LEVELING 
As a topographic feature the development of base-level 
terraces on the valley border is not so conspicuous within the 
Kern River area as it is at some points just outside of its 
limits. As shown in some of the photographs of the neigh- 
boring foot-hills, they form recognizable features along the 
southern border of the valley, and, as stated in former papers, 
they are present along its western border. Over the greater 
portion of the Kern River area, erosion has obscured or oblit- 
erated them to a considerable extent, though undoubtedly the 
mesa-like topography of the foot-hills is partly due to base- 
leveling, at least in its higher levels. 
On the south side of the Caliente Creek at about the altitude 
of Bealville is one of the more noticeable of these terraces. 
Terraces that are believed to be the result of base-leveling 
truncate the edges of the older Miocene beds to the north of 
the Kern River and Poso Creek, and also south of the river as 
far as the Tejon valley. 
GEOLOGY On Ge Poors 
The geology of the area as shown on the maps includes, 
broadly speaking, two series of rocks; the Neocene Tertiary 
and the basement series. This fact has been already mentioned 
by most of the writers who have alluded to this locality, and 
