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(5) Felsite and quartz porphyry dykes, much replaced by siderite,
occur only in the Cariboo series.

(6) There is an absence in the Slide Mountain series of large quartz
veins which are such characteristic features of the Cariboo series. ;

(7) The Mount Murray sills occur abundantly in the upper series and
very sparingly in the lower or Cariboo series.

(8) Placer gold was found in the Guyet conglomerate, but the bound-
aries of the rich placer fields of the area do not include any of the country
underlain by the Slide Mountain series.

GEOLOGICAL HISTORY

A definite sequence of events may be inferred from the previous account
of the geology and structure of the formations, but only one of the events
—the deposition of the Greenberry formation—can with any degree of
accuracy be fixed in the geological time record. Previous and subsequent
events can only be timed relatively to that period of deposition. The
general similarity of sequences and of lithological and structural rock types
in other better known districts may be used with caution to assign approxi-
mately definite times to these other events. This method has been adopted
to a considerable extent in the summary of the geological history which
follows.

PRECAMBRIAN (?) RECORD

The tentative assignment of the Cariboo series to a place in the Pre-
cambrian record is based on its general lithological and structural sim-
ilarity to the Beltian terrain elsewhere in British Columbia and to the fact
that the unconformity beneath the Slide Mountain series (Mississippian)
indicates that the Cariboo series was subjected to orogenic stresses, trans-
formed into schists, quartzites, and slates, intruded by dykes and sills and
considerably eroded prior to Mississippian time.

Richfield Epoch

The earliest events consisted of the deposition of coarse quartz sand
and fine quartz pebbles with a few layers of sandy and carbonaceous clay.
The subangular character of the grains of the rocks of this epoch, the
prevalence of iron oxide as a cementing material, the rapid variation
from fine to coarse grain, the occurrence of structures caused by contempor-
aneous erosion, and the great thickness of the series point to conditions of
continental deposition in localities of considerable relief. Whether the
high country from which the sediments were derived lay to the east or the
west could not be determined from a study of the local geology.

Barkerville Epoch

Deposition of the arenaceous sediments was followed by that of lime-
stones, containing numerous sandy and clayey beds, indicative of lower
relief and clearer water.