Facies architecture and stratigraphy of the Paleogene Huntingdon Formation at Abbotsford, British Columbia.

摘要

The Paleogene Huntingdon Formation is a succession of alluvial mudstone, sandstone, and pebble conglomerate preserved in southwest British Columbia, Canada. The study area includes the proposed type section of the Huntingdon Formation and is located in and near Abbotsford, British Columbia, Canada.; The Huntingdon Formation is correlative with, and continuous in the subsurface to, the Chuckanut Formation in northwest Washington State. The Huntingdon and Chuckanut formations were deposited in the Chuckanut basin during late Paleocene, Eocene, and possibly Oligocene time. The Chuckanut basin probably formed as a complex hybrid basin, reflecting the transpressive nature of the plate margin setting in this part of the Cordillera during Paleogene time.; In general sedimentary strata of the Huntingdon Formation dip gently towards the south and minor faults and multiple fracture sets are present. At Sumas Mountain (Canada) the remnant outcrops areas of the Huntingdon Formation are separated by a horst consisting of an unnamed igneous body. The orientation of brittle structures in a fault domain close to the horst suggests the related faulting did not occur until the middle Miocene.; Fluvial architectural element analysis and facies analysis of the type area indicates that this formation developed as a coarse, sand-dominated, terrestrial fluvial system, with an active floodplain. The range of features suggests proximal to distal transition from alluvial to braided to transitional sand-dominated meandering river systems. Paleocurrent analysis of the Huntingdon Formation indicates that it was sourced to the east. Sandstone and pebble conglomerate clasts are dominated by chert types, typical of first-order basin provenance from nearby Cascade oceanic terranes to the east.