The Jackass Mountain Group of south-central British Columbia: depositional setting and evolution of an Early Cretaceous deltaic complex1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.2Earth Science Sector (ESS) Contribution 20100280.

Abstract

The Lower Cretaceous Jackass Mountain Group of southwestern British Columbia records a complex history of deltaic and proximal marine sedimentation in a tectonically active area of the Canadian Cordillera. Two Jackass Mountain Group successions, exposed in the Camelsfoot Range and Chilko Lake regions and separated by ∼125 km across the northwest–southeast-trending Yalakom fault, provide details of stratigraphy, sedimentology, petrography, and geochemistry of the group. Restoring dextral movement across the Yalakom fault indicates that these locales were adjacent to one another during deposition; data presented herein support this reconstruction. In addition, detailed sedimentological investigations reveal widespread shallow-marine and deltaic features, indicating that deposition occurred predominantly within a large, shallow-water deltaic system. This interpretation is crucial to the understanding of regional facies patterns and for predicting hydrocarbon potential in adjacent subsurface rocks. New porosity, permeability, and thermal maturity data augment information collected from Jackass Mountain Group strata in the subsurface and indicate that some units represent potential hydrocarbon source rocks.