ENIGMATIC PHOSPHATIC TUBULAR FOSSILS FROM THE EARLY-MIDDLE PALEOZOIC BOUVETTE FORMATION, YUKON TERRITORY, CANADA

Phosphatization is an important taphonomic window into the early history of metazoan life in the Phanerozoic. Phosphatization mainly occurs in a window between the early Cambrian and the Early Ordovician. Additionally, it is strongly biased towards specimens that are relatively small, resistant to decay, and enriched with calcium phosphate.

Enigmatic phosphatic tubular fossils of Cambrian-Devonian age were found in the Bouvette Formation of Nadaleen Mountain in Yukon, Canada. The fossils were determined to be phosphatic using energy-dispersive X-ray spectroscopy (EDS). Many of these phosphatic microfossils are curved, hollow tubes with an average length of 2.07 mm and a diameter of .26 mm. They are accompanied by small, phosphatic circular fossils with small concave depressions in their center that appear throughout the sample with an average diameter of .18 mm. We interpret the tubes as body fossils as opposed to trace fossils since they display sharp breaks likely to be present only in body fossils, narrowing sections that contrast the widening sections of trace fossils, and a lack of crosscutting or evidence of bioturbation.

EDS analysis of the fossil-hosting matrix shows that it is non-phosphoritic, suggesting the organism created its own phosphatic microenvironment through decay, a rare process that was more common after the Early Ordovician than earlier examples of phosphatization. Further work on these tube-shaped and spherical fossils, including microscopic, microchemical, and morphometric analyses, can assist in determining their taphonomy and phylogeny and potentially shed light on the evolution of SSFs after the closing of the phosphatization window.