Highlights from the Middle Cambrian Stephen Formation
Chad A. Morgan, Ph. D. Candidate, Department of Geoscience, University of Calgary
Location: Mount Royal University, Room B108
Date: October 19, 2018, 7:30 pm
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The Middle Cambrian Stephen Formation has a long and storied history in palaeontology. The formation originally included the famous Burgess Shale lagerstätten found in Yoho National Park by Charles Walcott in the early 20th century, and has subsequently become one of the most internationally recognised rock units in western Canada. During this talk an introduction to the historic background and the current cutting-edge science surrounding this formation will be discussed from Walcott to Franco Rasetti, to ongoing research at the University of Calgary. Results on trilobite taxonomic reassessments and biostratigraphic analyses for the formation will be presented as well as newly discovered fossils, including ~505 Ma bacterial filaments, and unusual geometric trace fossils found in the 'platformal' (formerly thin) Stephen Formation. Additionally, a brief introduction to an as of yet unpublished and newly discovered Burgess Shale fossil site in Yoho National Park, which has yielded a large number of Margaretia dorus specimens will also be presented. This site with its large population of M. dorus specimens may aide in deciphering the taxonomic affinity of this problematic Burgess Shale fossil (whether they belong more closely with modern algae or are tubes constructed by hemichordate worms). While the Cambrian may not always have the most impressive large fossils found in Alberta, this talk will hopefully reveal the amazing array of exciting science currently being undertaken and still left to be done on the half billion year old record found in western Canada.
Chad Morgan is a PhD candidate in the Department of Geoscience at the University of Calgary. He is currently conducting research on trilobite biostratigraphy of the Middle Cambrian Stephen Formation under the supervision of Dr. Charles Henderson and co-supervised by Dr. Brian Pratt (University of Saskatchewan). His research has taken him to Burgess Shale fossil sites in Kootenay National Park as well as field sites in Yoho and Banff National Park. His research interests include invertebrate palaeontolgy, trilobite taxonomy, carbonate sedimentology, and ichnology.
In addition to the main presentation by Dr. Chad Morgan, Pete Truch will provide a brief presentation.
Ashfall Fossil Beds State Historical Park & National Natural Landmark Nebraska
Pete Truch is an APS member and a retired ardent traveler
The Yellowstone Hotspot (located in Yellowstone National Park) has produced five super-volcano calderas in the last 14 million years. The Bruneau-Jarbidge caldera resulting from the explosions of super-volcanoes between 12.5 and 10 million years ago have direct relevance to Ashfall, as this has been determined to be the source of the ash. Using single-crystal laser fusion Argon40/Argon 39 dating the tuff of the volcanic ash (with adjustment) yields a date of 11.93 million years. This one eruption is called the “Tuff of the Ibex Hollow”.
The ash (averaging one foot in depth) from this event blew into the hollow where a water hole was. Over time, the Ash Hollow Formation resulted, consisting of tan sandstone and grey-white ash, which varies in thickness from 3 to 5 feet. Captured in the ashbed, among other Pliocene critters, are fully articulated skeletons of rhinos Teleoceras major; camels Protolabis heterodontus; Procamelis grandis ; three toed horses Pseudhipparion gratum and one toed horses Pliohippus pernix.
Excavating and leaving the skeletal remains in situ resulted in a unique method of exposure within the confines of a large protective enclosed building. Thus, a visitor can see the bone beds and creatures exposed in their original mortuary poses, a number of which Pete will show in his summary presentation of a site visit made in 2017.
Pete and his wife Doreen are ardent travelers. In 2010, they joined the ranks of famous circumnavigators of the globe (in a ship) including Captain Cook’s goat who surpassed them by having done it twice! They have been on every ocean of the world (as Geographers have named them), although technically there is only one. In addition to having travelled to 68 countries, they have been in every jurisdictional part of Canada from Territories to Provinces, and now, with the visit to Ashfall Fossil Beds State Historical Park in Nebraska, have visited all 50 States.