LATE HETTANGIAN AMMONITE FAUNA FROM TASEKO LAKES

Taseko Lakes Region

The late Hettangian ammonite fauna of the Taseko Lakes region of British Columbia is among the most diverse, best preserved, and scientifically valuable Early Jurassic assemblages yet documented from western North America.

Over three field seasons between 2001 and 2003, researchers working in the Mineralense and Rursicostatum zones collected and systematically studied thirty-five ammonite taxa, resulting in the description of three new species: Fergusonites hendersonae, Eolytoceras constrictum, and Pseudaetomoceras victoriense. 

This expanded dataset significantly improves the precision and global applicability of the North American ammonite zonation for the Hettangian.

Taseko Fossil Field Camp

Among these discoveries, Fergusonites hendersonae—a new species of nektonic, carnivorous ammonite—was named in honour of Heidi Henderson by Dr. Louise Longridge of the University of British Columbia.

Henderson, who was serving as Chair of the Vancouver Paleontological Society at the time, had first met Longridge during Louise’s undergraduate years. She later played a significant role in expanding the Taseko Lakes collections, donating many of the specimens that are now part of the Geological Survey of Canada (GSC) collections.

Foundational Work of Dr. Howard W. Tipper (1931–2005)

Fergusonites hendersonae

The scientific framework that made the recent Taseko Lakes discoveries possible rests heavily on the lifetime work of Dr. Howard “Tip” Walwyn Tipper, one of Canada’s foremost Jurassic ammonite specialists.

Tipper served for decades as a field geologist and paleontologist with the Geological Survey of Canada, where he became renowned not only for his expertise in Early Jurassic ammonite taxonomy but also for his extraordinary skill as a regional mapper.

His geological maps of major tracts of the Canadian Cordillera remain foundational today; in some areas, they continue to serve as the base maps for modern projects nearly unchanged, a testament to his accuracy and observational skill.

Tipper dedicated much of his professional life to understanding the faunas and stratigraphy of the Chilcotin region and Haida Gwaii—areas he loved deeply. His work advanced global understanding of Jurassic paleobiogeography and helped establish the unique character of eastern Pacific ammonite faunas, which exhibit strong Tethyan affinities paired with high endemism.

Badouxia ammonites

Tipper published extensively on the biostratigraphy, taxonomy, and regional geology of the Western Cordillera. Tipper’s final years were spent sharing his vast knowledge with younger colleagues, ensuring a scientific legacy that continues to guide Early Jurassic research in western North America.

He passed away on 21 April 2005, leaving behind an unmatched body of work, a sharp wit, and a profound impact on his field. Tipper’s studies, especially in BC and Haida Gwaii, established the most robust framework yet developed for correlating eastern Pacific Hettangian faunas with global standards.

Smith’s later work with Longridge and others has continued to improve the precision of North American zonation, particularly through detailed analyses of Angulaticeras, Badouxia, and Sunrisites from Taseko Lakes.

Field Expeditions to Taseko Lakes (2001–2003)

The 2001–2003 field campaigns were undertaken with support from the Vancouver Island Palaeontological Society, the Vancouver Paleontological Society, and numerous researchers from the University of British Columbia. Dan Bowen and John Fam coordinated major elements of the expeditions.

Work in the Taseko Lakes region is demanding. Field teams endured high-elevation conditions, sudden weather shifts, persistent cold, and the occasional grizzly bear encounter. Nights were spent near glacial ice; days were often marked by rain or snow. Helicopter access dramatically shortened approaches to the high-alpine sections where late Hettangian strata are exposed.

These efforts yielded exceptional fossils: the three new ammonite species noted above, a beautifully preserved high-spired gastropod, and a lobster chela—all awaiting formal description.

Biostratigraphic and Global Correlation Significance

The Taseko Lakes fauna improves global correlation of Hettangian ammonite zones in several important ways:

1. The Mineralense and Rursicostatum zones are clearly present at Taseko Lakes and correlate well with strata across western North America.
2. These zones correspond broadly to the Canadensis Zone and likely the Arcuatum horizon in South America.
3. They correlate with middle–late Hettangian and earliest Sinemurian ammonite assemblages in New Zealand.
4. They align with the circum-Mediterranean Marmoreum Zone.
5. The Mineralense Zone and lower–middle Rursicostatum Zone correlate with the Complanata Subzone of north-west Europe, whereas the upper Rursicostatum Zone corresponds to the Depressa Subzone.

Such correlations are vital because global Hettangian biostratigraphy has long been complicated by strong provincialism and differing evolutionary trajectories. The Taseko Lakes fauna bridges these gaps by containing both highly endemic eastern Pacific taxa and cosmopolitan species that enable long-distance correlation.

Geological and Historical Context

Early work at Taseko Lakes was carried out by W. Frebold (1951, 1967), during a period when eastern Pacific ammonites were poorly understood and often forced into northwest European taxonomy. Since then, systematic studies across BC, Alaska, Alberta, the U.S. West Coast, Mexico, and South America (e.g., Guex; Imlay; Hillebrandt; Smith & Tipper; Riccardi; Jakobs & Pálfy; Taylor; Hall) have greatly expanded understanding of Jurassic faunas in the region.

Modern mapping by Schiarizza et al. (1997), Smith et al. (1998), and Umhoefer & Tipper (1998) has clarified local geology and stimulated renewed collecting, culminating in the comprehensive study by Longridge, Smith, and Tipper (2008). Additional taxonomic work on Sunrisites (Longridge et al., 2008) further enriches the dataset, though it remains to be fully integrated into North American zonation.

Hettangian Zonation: Improving the Global Framework

North-west Europe remains the global standard for Early Jurassic biochronology. However, rapid faunal turnover there—from schlotheimiid to arietitid dominance—differs markedly from more gradual transitions seen elsewhere. Endemism further complicates global correlation.

The Taseko Lakes fauna is therefore crucial:

• it provides rare overlap between Tethyan-affiliated and endemic eastern Pacific taxa;
• it enables direct links to volcanic sequences that allow radiometric calibration (Pálfy et al. 1999, 2000);
• and it strengthens intercontinental ties between North America, South America, New Zealand, western and eastern Tethys, and north-west Europe.

The correlation between Taseko Lakes and Nevada—another key late Hettangian locality—is of special interest.

Specimen and Locality Information

Fergusonites hendersonae Longridge et al., 2008

• Taxon number: PaleoDB 297415
• Family: Juraphyllitidae
• Dimensions: shell width 9.88 mm; diameter 28.2 mm
• Age: 201.6–196.5 Ma
• Locality: Taseko Lakes region, British Columbia (paleo-lat. 22.1° N, paleo-long. 66.1° W)

Holotype: GSC 127423

• Rursicostatum Zone, Castle Pass section A, level 06

Reference:

Longridge, L.M., Smith, P.L., & Tipper, H.W. 2008. Late Hettangian (Early Jurassic) ammonites from Taseko Lakes, British Columbia, Canada. Palaeontology 51: 367–404.