PALEOENVIRONMENTAL INTERPRETATION AND IDENTIFICATION OF THE NORIAN - RHAETIAN BOUNDARY IN THE WHITEHORSE TROUGH (STIKINE TERRANE, NORTHERN CANADIAN CORDILLERA)
We present two stratigraphic sections logged on Mt. Sinwa, located in the Northwest corner of British Columbia, and two more sections in the Whitehorse region of Yukon: Lime Peak and Hill 4308. Mt. Sinwa shows a facies progression consistent with a gradual shift from a back-reef to a reef crest setting near the top of the succession. Integrated conodont biostratigraphy and stable isotope chemostratigraphy constrains the placement of the Norian - Rhaetian boundary in both Mt. Sinwa sections, with the first occurrence of the Rhaetian conodont species Mockina mosheri coinciding with a negative δ13C excursion. This excursion can be correlated with those identified in sections spanning the Norian - Rhaetian boundary in the Tethys region. Strong covariance between δ13C and δ18O in both Yukon sections show that the primary δ13C signal has been lost, unlike the British Columbia sections. This discrepancy in the Sinwa and Aksala Formations could point to a difference in depositional positioning within the Whitehorse Trough, and/or a difference in diagenetic history. Through the integration of lithostratigraphy, chemostratigraphy, and biostratigraphy, this study paints a full picture of paleoenvironmental progression off the West Coast of North American during the Late Triassic and improves stratigraphic correlation between North America and the Tethys during this time interval.