8 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
post-Jurassic. On the other hand, the Franciscan is clearly pre-Knoxville; and the 
Knoxville has usually been regarded as the local base of the Cretaceous. Fossils are 
searce in the Franciscan, but such fragmentary forms as have thus far been found point 
to a Cretaceous age. It would seem not improbable, therefore, that the Franciscan 
represents a pre-Knoxville division of the Cretaceous, which has not as yet been recog- 
nized in the geological scale. The question, however, requires further investigation before 
a final decision can be reached. 
After the accumulation of the Franciscan strata as thus characterized, and perhaps 
in connection with the invasion of the series by peridotitic and basaltic intrusives, 
the region was folded and broken, and elevated within the zone of erosion. The 
elevatory movement was probably quite general. The Franciscan, while subjected to 
general denudation, was probably nowhere stript down to the underlying basal complex 
before it was submerged to receive the next succeeding sedimentary strata. These 
comprize the Knoxville formation, consisting wholly of shales and sandstones with quite 
subordinate layers and lenses of limestone, all in very regular and rather thin strata, 
significant of deposition in a shallow basin under fluctuating conditions of transportation. 
The Knoxville varies in volume from a few hundred to several thousand feet and is widely 
distributed over the Coast Ranges. It is succeeded in the vicinity of the Bay of San 
Francisco, and to a less marked degree in other parts of the Coast Ranges, by a formation 
of coarse conglomerate known as the Oakland conglomerate. This conglomerate attains 
a thickness of over 1,000 feet in places and follows the Knoxville shales in apparently 
conformable sequence. The change in the character of the deposits from shales to coarse 
conglomerates, without any interruption in the continuity of sedimentation, suggests 
an orogenic disturbance of the margins of the basin within which the Knoxville beds 
were accumulating, whereby the grades of the streams were greatly accentuated and the 
degradation of the continental region correspondingly accelerated. 
The Oakland Conglomerate, or, where that is missing, the Knoxville shale, is directly 
followed by a formation of thick bedded sandstones and shales known as the Chico 
formation. It has a thickness in places of many thousands of feet. The entire volume of 
strata, from the base of the Knoxville to the top of the Chico, is usually referred to as 
the Shasta-Chico Series, the Shasta comprizing the Knoxville and Oakland formations, 
together with certain other paleontological subdivisions not here particularly men- 
tioned. The series is remarkable for its great volume. In the northern Coast Ranges 
to the west of the Sacramento Valley, the thickness of the sedimentary section, com- 
prizing practically only sandstones and shales, is as much as 29,000 feet. This vast 
accumulation of strata clearly signifies the development of a great geosyncline, or depres- 
sion of the sea-bottom in that region in which deposition kept pace with subsidence 
thruout this portion of Cretaceous time. The Shasto-Chico series is usually regarded as 
comprizing the whole of the California Cretaceous, but the considerations cited above 
in regard to the Franciscan indicate that the latter may perhaps be included in the 
lower Cretaceous section of this region. 
The movements which brought the Mesozoic to a close and inaugurated the Tertiary 
in the Coast Range region were not those of violent orogenic deformation such as charac- 
terize this period of geological time in many other parts of the world; but were rather of 
the nature of a partial elevation of the region, with quite gentle deformation, resulting 
in a notable restriction of the basin of deposition. The earliest Eocene strata show no 
marked structural discordance with the Chico. It is nevertheless very probable that a 
notable unconformity exists, since the abundant and characteristic Cretaceous fauna 
disappeared and was supplanted by an almost totally distinct assemblage of life forms. 
The Eocene of the California Coast Ranges falls into two paleontologically distinct 
groups which have been classed together as the Karquines series. ‘The lower of these 
