Terminal Proterozoic stromatolite reefs with shelly fossils, Salient Platform, British Columbia.

摘要

The late Neoproterozoic Salient Platform (Byng Formation, upper Miette Group), located 50 km northwest of Jasper, Alberta, contains one of three known occurrences worldwide of the Cloudina-Namacalathus fossil assemblage.; The Salient Platform initiated in relatively deep water (minimum 30-50 m) on Mount Machray. Lowermost carbonates on Salient Mountain and The Colonel were deposited in quiet environments behind the developing stromatolitic reef. The upper two thirds of the platform formed in shallow water and consists of huge, elongated Platella and Cryptozoon bioherms, within which most shelly fossils are found. Carbonate production is terminated by Gog Group siliciclastic sedimentation. Thin, shell-bearing stromatolitic carbonates discovered within the lowermost Gog Group bring into question the current position of the Precambrian-Cambrian boundary in the southern Rocky Mountains (western Canada).; Petrographic and geochemical data indicate that the Salient Platform has undergone significant diagenetic alteration. delta13C values of microsparitic limestones appear to retain a primary isotopic signature, which correlates well with coeval late Neoproterozoic successions worldwide.