Recently I completed a trade (specimens to be shown in the next post) with Dan B. who sent me some interesting Cambrian Trilobite fossils from Tanglefoot Creek, BC, Canada. While I was preparing a post to show off some of the pieces he sent me, I asked him about the formation, it's geology and the history of the site. He directed me to several good resources and related a fair amount of personal knowledge as well. It was then that I decided that I was not the best person to write about these fossils since I had not collected them. I asked Dan if he'd like to write a blog post about them and he obliged with the following:
The McKay Group Trilobite Locality of Southeastern British Columbia.
Tucked away in the Southeastern corner of British Columbia not far from the historic town of Fort Steele, outcrops a highly fossiliferous exposure of the McKay Group. The site often referred to as the Tanglefoot Creek Trilobite Locality, for its location on an unnamed tributary of Tanglefoot Creek, is a very special place. Below are two photographs of the site.
Along the upper reaches of this creek lay the scattered remains of hundreds of oddly preserved trilobites from the Upper Cambrian (Upper Steptoean, 494.5-493 Ma). Odd is a perfect description for the mode of preservation of the Tanglefoot Creek trilobites, for each perfect trilobite is faithfully reproduced by vertical encrustations of parallel to sub-parallel crystals of calcite that have grown from the dorsal and ventral surfaces of the trilobite. These calcitic growths form neat little wafers that weather from the marly limestones exposed at the site. Occasionally these calcite wafers grow together forming sheet-like structures. Although this mode of preservation is strange it is reminiscent of that of the Middle Cambrian trilobites found in the Wheeler Formation of Utah, however those trilobites do not occur on wafers.
Typical calcite wafers.
Several wafers that have grown together. Wujiajiania sutherlandi.
Complete trilobites are a rarity at most Cambrian sites but at the Tanglefoot Creek site the vast majority of specimens are either fully complete (i.e. carcasses) or missing their free cheeks (i.e. moults). Partial specimens do occur but the large numbers of complete specimens overshadow these.
Large wafer with Labiostria westropi.
The trilobite fauna at Tanglefoot Creek shows a fair amount of diversity. There are ten genera with 11 species commonly found at the site. By far the most common species encountered are Wujiajiania sutherlandi and Labiostria westropi.
The next most commonly encountered species are Pterocephalia norfordi, Irvingella major and Pseudagnostus communis.
Two specimens of Irvingella major
The remaining species (Hedinaspis canadensis, Elvinia roemeri, Irvingella new species, Agnostotes clavata, Aciculolenus palmeri and Burnetiella leechi) are less frequently encountered.
Additionally there are very rare specimens of Homagnostus sp. and Cliffia c.f. lataegenae . As these species are rarely encountered, I do not have photos of either specimen.
Since the publication of the site's location by researchers at the University of Alberta (B.D.E. Chatterton) and Denman Island (R. Ludvigsen) in 1998 the area has been staked as a mineral lease. As such collecting is no longer allowed at the site but numerous other localities nearby have been found outside the lease area. These new sites rival the original Tanglefoot Creek locality in terms of trilobite diversity. Current research on these new sites and their associated trilobite faunas is being undertaken at the University of Alberta and a paper is forthcoming.
For further information on this remarkable locality and its trilobite fauna see the sources below.
Brian D.E. Chatterton and Rolf Ludvigsen. 1998. Upper Steptoean (Upper Cambrian) Trilobites from the McKay Group of Southeastern British Columbia, Canada. Memoir 49, The Palaeontological Society, 43 pages.
Carlo Kier's collection of Tanglefoot Creek Trilobites including photos of some of the new species currently being investigated.
Chris Jenkins' collection of Tanglefoot creek trilobites mainly from the new sites.
If you would be interested in more information about this site and the fossils found there, feel free to contact Dan at: Palaeopix(at)gmail.com