On the east side of North Barriere River 6 kilometres north of the confluence of the Barrier River. The limestone on the north side of the Baldy Batholith, outcropping just north and south of Vavenby on either sides of the North Thompson River. The unit is commonly estimated to be up to several hundred metres thick.

The Tshinkan limestone is comprised prominently of light grey to white, massive, fine-grained limestone that is sometimes interbedded with quartzite and pyllite. The unit is rarely dolomitic.