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TitleNew occurrences of Oldhamia in eastern Yukon, Canada: stratigraphic context and implications for Cambrian deep-marine biostratigraphy
AuthorMacNaughton, R BORCID logo; Moynihan, D P; Roots, C F; Crowley, J L
SourceIchnos: An International Journal For Plant and Animal Traces vol. 23, no. 1-2, 2016 p. 33-52,
Alt SeriesEarth Sciences Sector, Contribution Series 20150359
PublisherInforma UK Limited
Mediapaper; on-line; digital
File formatpdf
NTS105O; 105J
AreaSelwyn Basin
Lat/Long WENS-132.0000 -130.0000 64.0000 62.0000
Subjectsgeochronology; marine geology; paleontology; regional geology; stratigraphy; chronostratigraphy; index fossils; paleobiology; invertebrates; fossil distribution, strata; marine deposits; biostratigraphy; Selwyn Basin; Cambrian
Illustrationslocation maps; geologic maps; stratigraphic cross-sections; photographs; graphs; tables
ProgramGEM2: Geo-mapping for Energy and Minerals Mackenzie Corridor, Shield to Selwyn
Released2016 03 16
AbstractFor over a century, the ichnogenus Oldhamia has been used as an index fossil for Cambrian deep-marine siliciclastic successions. New specimens from the Cambrian of Selwyn Basin, eastern Yukon, Canada, provide an opportunity to constrain the chronostratigraphic range of Oldhamia and test its potential for more detailed biozonation. The upper part of Narchilla Formation (Arrowhead Lake Member) yields O. antiqua, O. curvata, O. flabellata, and O. radiata. The overlying Gull Lake Formation yields a less diverse assemblage of O. antiqua, O. curvata, and O. flabellata. The upward disappearance of O. radiata is consistent with models that infer increasing complexity of Oldhamia ichnospecies through time but may also be a function of limited sampling. Regional stratigraphic correlations suggest Oldhamia appeared in Arrowhead Lake Member during Cambrian Stage 3. Archaeocyathans and trilobites from Gull Lake Formation confirm that Oldhamia was present during Cambrian Stages 3 to 4. A younger age limit on Oldhamia in Selwyn Basin is provided by synvolcanic detrital zircons recovered from the base of the overlying Old Cabin Formation, which yield an age of 499.89 § 0.14 Ma (earliest Guzhangian). Oldhamia appears to be a reliable index fossil for Cambrian Series 2 and Series 3 in Selwyn Basin.
Summary(Plain Language Summary, not published)
Manuscript reports new occurrences of fossilized burrow networks from ancient rocks in eastern Yukon that were deposited in a deep-marine basin. The burrow networks are collectively referred to by the name "Oldhamia". Oldhamia has long been known to to indicate that rocks containing it probably were deposited during the Cambrian Period of Earth history (485-542 million years ago), but the time range of Oldhamia within the Cambrian is more controversial. We are able to show that Oldhamia first appeared more than 20 million years after the start of the Cambrian and had disappeared after another 20 million years. As a result, Oldhamia can now be used as a well-constrained "index fossil" for dating deep-water Cambrian rocks in NW Canada.

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