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Significant advancements in understanding the complex evolution of the Tofino Basin at a convergent accretionary margin are enabled by combining contextual geologic information with new isotopic and paleontological data. A high-resolution Cenozoic chronostratigraphy of the basin is constrained by strontium isotope ages (36.9–1.3 Ma) of Late Eocene to Pleistocene foraminifers together with a revised biostratigraphy (foraminifers and ichthyoliths) from six offshore wells and outcrop samples, new specimen thermal alteration values, and existing well log data. These data are integrated with archival multichannel seismic and magnetic data to interpret offshore well positions with relation to sub-basins and structural highs of the Pacific Rim and Crescent terranes, and other accreted strata. Six regions of the Tofino Basin are defined based on structure and depositional differences during the Eocene to Holocene …