Abstract

The succession of metasedimentary rocks in the Riondel area is correlated with a Hadrynian–Cambrian sequence established in the Duncan Lake area to the north and the Salmo area to the south. The succession includes phyllite, schist, and quartz-pebble conglomerate of the Horset hie f Creek Group; quartzite, siltstone, and schist of the Hamill Group; calcareous schist of the Mohican Formation; and a prominent marble, the Badshot Formation. The youngest metasedimentary rocks include para-amphibolite, calc-silicate gneiss, and pelitic schist of the Lardeau Group.A lower Paleozoic succession of metasedimentary locks in the western part of the Riondel area forms a large overturned panel which is the lower limb of a phase 1 recumbent anticline, the 'Riondel nappe'. The root zone of the nappe is inferred to lie beneath a west-dipping reverse fault, the 'West Bernard fault', which separates the inverted panel of rocks on the west from the right-way-up panel in the east. Tight to isoclinal north–south trending phase 2 folds with upright to west-dipping axial surfaces and sub-horizontal fold axes are superposed on the Riondel nappe. Small-scale, south westerly trending phase 3 warps and open folds are overprinted on the limps of the older folds.The age of the Riondel nappe cannot be positively determined. It is assumed to have developed during the Caribooan orogeny in Devono-Mississippian (?) time and subsequently to have been deformed by phase 2 folding and associated faulting in middle Jurassic to early Cretaceous time.

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