GEOLOGY OF THE SOUTHERN COAST RANGES 559 
be bunch-like or eliptical in form, sometimes 100 feet thick 
and several hundred feet long, and from this size down to those 
only a few inches in thickness. Where the inclosing rocks 
are exposed they invariably lie in contact with one of the fine 
grained basaltic intrusives. Glaucophane gives the characteris- 
tic bluish tint, but other minerals, such as a pearly mica, 
chlorite, quartz and garnet occur. These rocks possess great 
interest though the problems connected with their occurrence are 
not yet all solved. There can be little question that they have 
been formed through the metamorphosis of argillaceous strata 
in contact with igneous masses, but why this action was so 
irregular and intermittant it is difficult to comprehend) lt 1s 
also puzzling to know why the contact rocks are invariably 
associated with a certain type of the pre-Cretaceous basic 
intrusives and not with others, such as the peridotites:.. ihe 
exceeding abundance of the contact rocks through those areas 
of the Golden Gate series where the old eruptives are the most 
numerous, indicates plainly that the most if not all the latter are 
of subsequent origin. 
CRETACEOUS PERIOD. 
Knoxville Beds —The rocks of lower Cretaceous age are now 
confined to the Santa Lucia range, although once probably much 
more extensive. They form an almost continuous strip from the 
head of the Corral de Piedra Creek on the south slope of the 
Santa Lucia range northwest for a distance of over twenty miles. 
North of Cuesta Pass they widen out forming for a number of 
miles nearly the whole of the brush-covered mountains between 
the two crests of the range. The structure of this portion is 
synclinal and seems to be due to the intrusion of great masses 
of diabase along its edges and which form the double crests 
referred to. The beds are perhaps 3000 feet thick and consist 
of dark shales and thin bedded sandstones closely resembling 
those of the same age in other parts of the state. Several thin 
layers of pebbly conglomerate occur, one being at the base and 
containing numerous pebbles of jasper and other silicious rocks. 
