New Occurrences of Oldhamia in Eastern Yukon, Canada: Stratigraphic Context and Implications for Cambrian Deep-Marine Biostratigraphy.

For over a century, the ichnogenusOldhamiahas 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 ofOldhamiaand test its potential for more detailed biozonation. The upper part of Narchilla Formation (Arrowhead Lake Member) yieldsO. antiqua, O. curvata, O. flabellata, andO. radiata. The overlying Gull Lake Formation yields a less diverse assemblage ofO. antiqua, O. curvata, andO. flabellata. The upward disappearance ofO. radiatais consistent with models that infer increasing complexity ofOldhamiaichnospecies through time but may also be a function of limited sampling. Regional stratigraphic correlations suggestOldhamiaappeared in Arrowhead Lake Member during Cambrian Stage 3. Archaeocyathans and trilobites from Gull Lake Formation confirm thatOldhamiawas present during Cambrian Stages 3 to 4. A younger age limit onOldhamiain Selwyn Basin is provided by syn-volcanic detrital zircons recovered from the base of the overlying Old Cabin Formation, which yield an age of 499.89 ± 0.14 Ma (earliest Guzhangian).Oldhamiaappears to be a reliable index fossil for Cambrian Series 2 and Series 3 in Selwyn Basin. [ABSTRACT FROM AUTHOR]