The City of Kamloops lies in the middle of the Quesnel Terrain. The Quesnel Terrain
main units consist of the Harper Ranch Group, the Nicola Formation, the Kamloops
Group plus some intrusive rocks.
The Kamloops Group are one of the youngest group of rocks in the Kamloops area. Predominantly,
these rocks are basalt's and andesites, often forming plateaus. There are some sedimentary
rocks associated with this group.
The Nicola Group are older rocks than the the Kamloops Group and consist of both
volcanic and sedimentary rock. The volcanic's are basalt's and andesites with the
sedimentary rocks ranging from shale to mud and sandstone.
Older than the Nicola Group is the Harper Ranch Group. The Harper Ranch Group is
composed mainly of sedimentary rocks. These rocks include argillite, siltstone,
sandstone, conglomerate and some carbonates (such as limestone).
The intrusive's found in the area intrude the Nicola Group and lesser the Harper
Ranch Group. There are three main locations of the intrusive's, the Wild Horse Batholithic
(East of Stump Lake), the Nicola Horst (between Stump Lake and Logan Lake) and the
Guichon Batholithic (West of Logan Lake and host to the Highland Valley Cooper Mine).
Generally, these intrusive rock are granitic.
There is an abundance of rock hounding sites around Kamloops. A few examples of
interesting specimens that can be found in the local host rocks are:
The Kamloops Group volcanic rocks are a great source of agates
Limestone from the Harper Ranch Group may have crinoid fossils
Sulphide minerals (chalcopyrite, pyrite) may be found associated with the various
intrusive rocks in the area
Reference: Geological Survey of Canada Open File 6659, BC Government MapPlace
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