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Kamloops Geology

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 Kamloops Group and consist of both volcanic and sedimentary rock. The volcanic’ s are basalt’s andesites and 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 so in the Harper Ranch Group. There are three main locations of 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 Copper Mine). Generally, these intrusive rocks 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