An Expanded Record of Ediacaran Chemostratigraphy from the Windermere Supergroup, Cariboo Mountains, British Columbia, Canada

Ediacaran strata (635-540 Ma) record the sudden appearance and diversification of large animal life in the fossil record. As a result, multiple studies have attempted to link both evolutionary innovations and environmental changes as drivers for the initial diversification of Ediacaran organisms and their eventual extinction at the Precambrian-Cambrian boundary. However, such inferences rely on recognition of correlative strata between different successions to rigorously compare environmental and evolutionary change with accurate measures of diversity in the fossil record. Unfortunately, most Ediacaran organisms have limited biostratigraphic utility, therefore only chemostratigraphic and geochronometric data can reliably correlate units. These data remain limited, leaving major chronological gaps in our subdivision of the Ediacaran timescale. Here, we present new lithostratigraphic and carbonate carbon isotope (δ¹³C_carb) chemostratigraphic data from Ediacaran-aged slope and platformal rocks of the Windermere Supergroup in the Cariboo Mountains, B.C., Canada. These data establish new correlations for formations within the Cariboo Group (Isaac, Cunningham, Yankee Belle, and Yanks Peak) to equivalent strata around the world, and compare the location Ediacaran-Cambrian boundary in the Cariboo Mountains to Windermere Supergroup strata preserved elsewhere in the Canadian Cordillera. Sedimentological and isotope data along with ichnological data also suggest the sub-Cambrian unconformity occurs at the contact between the Cunningham and Yankee Belle Formations, below the traditional interpretation of the Ediacaran-Cambrian boundary between the Yankee Belle-Yanks Peak transition in the Cariboo Mountains. Furthermore, chemostratigraphic data are interpreted to record enriched post-Gaskiers Glaciation isotopic values succeeded by a negative excursion interpreted to be the Shuram-Wonoka anomaly in deep-water slope facies, overlain by extensive platformal deposits which record the late Ediacaran positive high. Together, these data represent an archive for correlating Ediacaran deposits throughout the ancestral western Laurentian margin, and add important temporal constraint on global stratigraphic successions that are essential to establishing the Ediacaran timescale.