Since the 1970s, usage of ichthyoliths (microscopic fish teeth, scales, dermal denticles) for biostratigraphic studies has expanded from Cenozoic deep-sea core studies to those that include other environments and ages in the Cenozoic, Mesozoic, and Paleozoic (Table 1). Ichthyoliths have a calcium phosphate chemistry that makes them more resistant to dissolution than many other fossils and a heavier specific gravity than many sediment particles, resulting in their concentration under certain depositional conditions. These factors offer new opportunities to better understand sedimentary processes, and date and correlate strata where ichthyoliths and not other fossils may be present. In this study, identifying, describing, and illustrating Tofino Basin ichthyoliths is the first stage for biostratigraphic study. The next stage follows with interpreting fossil ranges and environments, geology, and dating and correlating marine Tofino Basin strata. These data and interpretations are important to build basin models for assessing petroleum potential in the Tofino Basin, British Columbia.

This paper and catalogue include identification, description, and illustrations of 99 species, forms, or subtypes (17 new) of in situ upper Eocene to Pliocene and transported/reworked Cretaceous-Eocene Tofino Basin ichthyoliths. Some of the elasmobranch (shark) ichthyoliths are identified from the families Lamnidae, Scyliorhinidae, and Rajidae and Superorder Squalomorphii. Several of the Oligocene and Miocene Tofino Basin ichthyoliths are compared with similar faunas and stratigraphic intervals in deep-sea core sediments.

Tofino Basin ichthyoliths are correlated with foraminifers from the same samples and are correlated with other Pacific Northwest and Arctic foraminifer zones. With this foraminifer stratigraphic, age, and paleoenvironment control and also correlation with dated deep-sea ichthyoliths, distinct Tofino Basin indicator ichthyoliths are recognized for upper Eocene to Pliocene intervals (Figure 2.2).

Additional ichthyolith materials (slides from 200-300 samples) were reviewed from the Queen Charlotte and Nanaimo basins when potentially reworked Cretaceous ichthyoliths were discovered in some of the Tofino Basin samples. The specimens provide comparative identification materials and will contribute important data for analysis of basin processes and stratigraphic correlation.

Identifying and naming disarticulated fish teeth, scales, and dermal denticles is a common problem. The coded utilitarian ichthyolith identification system (CUIIS), developed by Doyle et al. 1974, provides a method to identify ichthyoliths and proceeds with biostratigraphic studies. Since its inception, modifications and updates to the system have been documented by many users of the system. In this paper, the coded system is used, further modifications are made to include new Tofino Basin subtypes, and the part relevant to Tofino Basin ichthyoliths is included herein and digitized (Appendix 1). Through electronic publishing we are testing its application. The electronic media allows use of the key and provides a link to the taxon illustration and description that are together on one or two pages in the catalogue. Because the catalogue is digitized, the user can reorganize it to their preference.

Tofino Basin ichthyoliths are grouped into elasmobranch teeth, elasmobranch dermal denticles, triangular teeth with canals, triangular flanged teeth, triangular flexed teeth, cone teeth, and other ichthyoliths. Within each group, the ichthyoliths have some morphological similarities. Differences between groups may represent functional differences (e.g., dermal denticles, scales, and teeth) and/or differences in species. However, until articulated fossil fish are found which allow confirmation of the association of different ichthyoliths, associations remain speculative.

Some ichthyolith morphologies are known to occur in certain Mesozoic-Cenozoic fishes such as elasmobranch teeth and dermal denticles, and actinopterygian cone teeth. The distribution pattern of Tofino Basin ichthyoliths indicates: 1) a predominance of elasmobranch dermal denticles and teeth from reworked Cretaceous-lower Cenozoic intervals; and 2) in situ ichthyoliths such as teeth with canals, flexed teeth, and some elasmobranch teeth and dermal denticles in upper Eocene and Oligocene strata. In the Miocene interval, the older faunas are replaced by mainly actinopterygian (teleost) cone teeth. The reworked Cretaceous ichthyoliths and the faunal change across the Oligocene/Miocene interval corresponds to regional geologic and tectonic activity that affected water depth, environments, and strata within the Tofino Basin. In addition, a global climatic cooling trend was occurring from the Oligocene through Pleistocene.

Over 3,100 onshore outcrop and offshore subsurface samples are used in this study. Rare but moderately diverse ichthyoliths are indicated mainly in fine-grained shale, mudstone, and siltstone samples of bathyal environments. Three coarser-grained (lag or turbidite) outcrop samples contain common and reworked Cretaceous-Eocene ichthyoliths from proximal or nearshore environments. Future sampling for ichthyoliths in certain coarser-grained sediments may produce additional important fossils and data to interpret sedimentary basin and geological processes.