Abstract

Detailed descriptions and stratigraphic analysis of 159 species of foraminifers recovered from six existing wells drilled in the Tofino Basin, offshore Vancouver Island support the establishment of 10 zones, ranging from upper Eocene to Pleistocene-Recent. The newly refined stratigraphic ages improve correlations between the offshore Tofino Basin and onshore outcrops of the Carmanah Group on western Vancouver Island and to other areas in the Pacific North-west and Canadian Arctic.

Paleobathymetric estimates from interpreted biofacies changes indicate a shallowing upward trend throughout the Oligocene, with deep biofacies encountered during the early Miocene and early Pliocene, reflecting a major transgression or basin subsidence. Late Pliocene-Pleistocene inner to outer neritic biofacies, cool-water faunal assemblages and coarser-grained lithology indicate a regressive phase and regional onset of glaciation.

The TB represents a complex tectono-stratigraphy, which has undergone episodic uplift, tectonic underthrusting, climatic cooling and eustatic fluctuations resulting in complex facies changes, stratigraphic breaks and structural complexities. The new, updated biostratigraphy has constrained many of these regional geological events, with improved/high resolution analysis of correlations and paleoenvironmental interpretations. Proposed lifting of federal and provincial moratoriums on offshore exploration and development has renewed interest in offshore energy resource potential, reassessment of existing data, and interpretations of the Tofino Basin (TB) and adjacent shelf architecture. This study provides baseline data for future taxonomy, biostratigraphy, basin modeling and energy resource assessments.

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