Extensive bioturbation in a middle Cambrian Burgess Shale–type fossil Lagerstätte in northwestern Canada

Abstract

Research Article| January 18, 2019 Extensive bioturbation in a middle Cambrian Burgess Shale–type fossil Lagerstätte in northwestern Canada Brian R. Pratt; Brian R. Pratt 1Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada Search for other works by this author on: GSW Google Scholar Julien Kimmig Julien Kimmig 2Biodiversity Institute, University of Kansas, Lawrence, Kansas 66045, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Brian R. Pratt 1Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada Julien Kimmig 2Biodiversity Institute, University of Kansas, Lawrence, Kansas 66045, USA Publisher: Geological Society of America Received: 03 Sep 2018 Revision Received: 04 Jan 2019 Accepted: 04 Jan 2019 First Online: 18 Jan 2019 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2019 Geological Society of America Geology (2019) 47 (3): 231–234. https://doi.org/10.1130/G45551.1 Article history Received: 03 Sep 2018 Revision Received: 04 Jan 2019 Accepted: 04 Jan 2019 First Online: 18 Jan 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Brian R. Pratt, Julien Kimmig; Extensive bioturbation in a middle Cambrian Burgess Shale–type fossil Lagerstätte in northwestern Canada. Geology 2019;; 47 (3): 231–234. doi: https://doi.org/10.1130/G45551.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Mudstones hosting Burgess Shale–type preservation of soft-bodied fossils are commonly held to be characterized by little to no bioturbation. This has been taken as evidence for bottom-water dysoxia or anoxia, along with anaerobic conditions in the sediment, which favored preservation of soft tissues by hindering decay. Although invisible on fresh and weathered surfaces, laminated claystone comprising the middle Cambrian (Drumian) Ravens Throat River Lagerstätte in the Rockslide Formation of the Mackenzie Mountains, northwestern Canada, is revealed by preparation of surfaces sawn parallel to bedding to exhibit extensive burrowing. Four types of burrows are distinguished: (1) rare large forms averaging 15 mm in diameter; (2) backfilled vertical burrows 3–6 mm wide; (3) oblique to horizontal burrows 2–4 mm wide and typically with meniscate backfilling; and (4) tiny, short, mostly vertical burrows 0.5–1 mm in diameter. The third group is the most common, locally completely bioturbating laminae and penetrating worm carcasses; it conforms to Planolites. A variety of ethologies is indicated, with the large type seemingly serving as a dwelling burrow and the smaller ones from deposit-feeding. Although dysoxic bottom conditions probably developed occasionally, the widespread burrowing argues for predominantly oxic conditions, and it indicates that restriction of bioturbation was probably not the most important factor leading to soft-tissue preservation. Bioturbation might be more common in other Cambrian Lagerstätten than is currently believed, and it is possible that low-oxygen conditions at the seafloor were not fundamentally necessary for Burgess Shale–type preservation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.