diller.] TOPOGRAPHIC DEVELOPMENT OF KLAMATH MOUNTAINS. 47 
AGE OF KLAMATH PENEPLAIN. 
That the sediments of the Neocene beds deposited along the sea- 
ward border of the Klamath peneplain were derived from the Klamath 
Mountain region there can be no reasonable doubt. They record a long 
period of but little relative movement of land and sea, during which 
the land suffered extensive degradation and was finally reduced 
approximately to a peneplain. That there were changes of level 
during the Neocene sufficient to record themselves in a marked 
change of sediments is clearly shown by the presence of heavy beds 
of conglomerate among the sandstones and shales at Cape Blanco and 
later in the region of Humboldt Bay, but on the whole the sediments 
were derived from land areas of low declivity. The rich fauna and 
the calcareous nodules suggest the same condition. 
The condition whieli the Wymer beds record is that of the Kla- 
math peneplain just before it was uplifted to initiate the plateau of 
the Klamath Mountains. The Wymer beds are purely marine sedi- 
ments, resting upon the very edge of the Klamath peneplain, and now 
lie practically undisturbed, except for the uplifting to their present 
altitude of 2,200 feet. They are possibly east of the zone of greatest 
displacement connected with the final uplifting of the Klamath 
Mountains. 
Beds of nearly the same relative position occur at an elevation of 
1,350 feet about the eastern limit of the Neocene beds in the vicinity 
of Bridgeville. Except where indurated by local deposits of car- 
bonate of lime the beds are very soft and lie undisturbed east of the 
belt of greatest disturbance of the Wildcat series. According to Dr. 
Dall, all the fossils found in the Neocene strata about Bridgeville are 
Miocene species. 
While it is certain that the deiDosition of the Wymer beds and those 
of the hills about Bridgeville occurred during the Neocene and prob- 
ably in the late Miocene, its exact geological age can not be fully 
established without further paleontological study and comparison 
with the various formations developed about San Francisco Bay and 
Ithe adjoining portion of the Great Valley of California. The age 
of the San Pablo beds, of which Dr. Dall has made mention, is not 
definitely known, or at any rate its fauna has not as yet been fully 
published. The tendency of the evidence throughout, as far as 
known, appears to indicate a late Miocene age for the Klamath 
peneplain, but if on further study the Wymer beds and those of the 
Hay Fork stage should turn out to be Pliocene or Pleistocene the age 
of the Klamath peneplain would be correspondingly reduced. 
DISLOCATION OF MIOCENE DEPOSITS OF COAST RANGE 
AND SUBSEQUENT PLANATION. 
Although there were slight variations in the relative attitude of the 
and and sea during the Miocene, as recorded in the change of sedi- 
