CARD

Locality: right bank of Old Crow River, Old Crow Basin, Porcupine drainage, northern Yukon Territory
Map sheet: 117 B/08

Significance: geochronology, anomalous, young; géochronologie, anormal, jeune
Context: alluvium, lower Unit 2a
Associated taxa: Mammalia: Mammuthus sp

Additional information: AMS date. Collagen extraction method 3, >30kD; this is a suspect date as the sample had none of the properties of well-preserved collagen.
Comments: NbVn-4, Old Crow River Locality CRH-47: RIDDL-733 is difficult to interpret. The mammoth mandible was recovered from a fluvial channel fill in lower unit 2a near the downstream end of the section in association with the left and right lower molars of Mammuthus armeniacus. A water-screened sample of the enclosing matrix contained some relatively primitive microtine rodent taxa, including Microtus deceitensis and Phenacomys deeringensis, implying potentially great antiquity. Unfortunately, the top of the channel could not be traced to an associated floodplain, rendering it difficult to establish correlations between the channel fill and other exposures along the section. Surprise Creek tephra outcrops in lower unit 2a at the upstream end of the section. Its age has been established at 180,000 +/- 80,000 years by fission track analysis, and it may be younger or older than the mammoth bone dated by RIDDL-733. Finally, despite the use of the presumed best method of collagen extraction, isolating nominal molecular weights >30kD, the recovered material had none of the characteristics of well preserved collagen, rendering the date suspect regardless of the contextual data.

Canada / YT / NbVn-4 (Old Crow Loc. CRH-47) / RIDDL-733