Burgess Shale

First Glimpse of the Cambrian Explosion

The Burgess Shale is a very famous fossil Lagerstätte named after the nearby Burgess Pass. This site is high in the Canadian Rockies within Yoho National Park near the town of Field, British Columbia, Canada. The Burgess Shale was discovered in 1909 by famed paleontologist Charles Doolittle Walcott, who returned time and again to extensively study its fossils. Walcott described a large diversity of previously unknown arthropods, and most importantly many forms of previously unknown phyla as well as many forms that remain enigmatic today. The fossils were particularly important at the time to understand Cambrian paleobiology because of their often exquisite preservation that included soft body parts. Many such Cambrian sites have since been discovered, most notably the Chengjiang Maotianshan Shales, which are collectively called sites with Burgess Shale-like preservation.

The Burgess Shale fossils are about 505 million years old, some 20 million years younger than those from Chengjiang. In fact, the Burgess Shale and Chengjiang have considerable overlap in faunal forms. Less well known is that Cambrian formations in the House Range of Utah yield many fossils like the Burgess Shale, though the soft tissue preservation is usually not as good. The Burgess Shale Formation comprises 10 separate members, the most famous being the Walcott Quarry Shale Member comprising the greater phyllopod bed.

The Burgess Shale comprises shale, limestone and siltstone and extends in a large area in outcrops of the Stephen Formation that exhibite different faunal mixes. The fossils of the Burgess Shale are preserved as black carbon films on black shales. Scientists long believed the deposits were formed when areas of muddy ocean floor slid into a lower place creating an anoxic (oxygen-starved) environment that was particularly favorable to fossilization because decay was inhibited. More recent research that oxygen was continually present in the sediment

While there are older Cambrian Lagerstatten, the Burgess Shale was science's first glimpse of the Cambrian Explosion in the fossil record. The extensive diverse fauna generally new to science and their often exquisite soft-bodied preservation, caused Walcott him to return repeatedly to the fossil site until 1924. By age 74 he had amassed more than 65,000 specimens. Describing the fossils was a vast task the Walcott continued until his death in 1927. Walcott, influenced by the opinion of scientific peers, tried to associate the fossils with living taxa, which delayed the scientific significant of them to be delayed by serveral decades. Three decades of study commencing in the 1960's led to the Burgess Shale ultimately attaining the recognition of today as a remarkable rock record of early Cambrian life and its early diversification.

Burgess Shale Fossils
Partial List of Burgess Shale Fauna Phylum Annelida Canadia Phylum Arthropoda Burgessia Canadaspis Elrathina (trilobite) Leanchoilia Marella Naraoia Olenoides (trilobite) Perspicaris Ptychagnostus (trilobite) Sidneyia Waptia Yohoia Phylum Brachiopoda Micromitra Phylum Chordata Pikaia Phylum Ctenophora Ctenorhabdotus Fasciculus Xanioascus	Phylum Hyolitha Haplophrentis Phylum Mollusca Scenella Phylum Onychophora Aysheaia Hallucigenia Phylum Porifera Choia Phylum Priapulida Ottoia Phylum Incertae sedis Amiskwia Anomalocaris Dinomischus Nectocaris Odontogriphus Opabinia Orthrozanclus Wiwaxia
		Leanchoilia superlata Phylum Arthropoda Stephen Formation Burgess Pass	Naraoia compacta Phylum Arthropoda Stephen Formation Burgess Pass
Ptychagnostus praecurrens Class Trilobita Order Agnostida Family Ptychagnostidae Stephen Formation Burgess Pass	Marella splendens Phylum Arthropoda Order Marrellomorpha Stephen Formation Burgess Pass	Micromitra burgessensis Phylum Brachiopoda Family Paterinatidae Stephen Formation Burgess Pass	Ottoia prolifica Phylum Priapulida Family Ottoidae Stephen Formation Burgess Pass
Burgessia bella Phylum Arthropoda Family Bugessiidae Stephen Formation Burgess Pass	Elrathina (= Ptychoparella) cordillerae Mass Mortality Class Trilobita Order Ptychopariida Family Alokistocaridae Walcott Quarry Shale Member	Scenella amii Phylum Mollusca (?) Family Scenellidae Stephen Formation Burgess Pass	Canadaspis perfecta Phylum Arthropoda Family Canadaspididae Stephen Formation Burgess Pass