SEDIMENTOLOGY, ICHNOLOGY, AND SOFT-BODIED PRESERVATION OF THE SERIES 3 CAMBRIAN MARCH POINT AND PETIT JARDIN FORMATIONS, WESTERN NEWFOUNDLAND

The Series 3 March Point Formation exposed on the Port au Port peninsula, western Newfoundland is a mixed carbonate-siliciclastic succession deposited during Sauk II transgression. It preserves body and ichnofossils that provide important insights into equatorial paleoenvironments and paleoecology of southeastern Laurentia during middle Cambrian time. The March Point Formation is overlain by the dominantly siliciclastic Cape Ann Member of the Petit Jardin Formation, and acid macerates of shales from both units yield soft-bodied fossils, such as priapulid worm scales and arthropod cuticle.

March Point Formation transitions from primarily siliciclastic facies near the base (dominated by shales and sandy limestones) to more carbonate-rich strata up-section. These basal shales preserve the first soft-bodied fossils of this unit. In the upper March Point Formation and lower Cape Ann Member, parted limestone becomes increasingly shale-rich until the entire section is dominated by shale. Abundant soft-bodied fossils have also previously been found in this shale facies. Trace fossils, such as Gordia, Thalassinoides, and Diplocraterion are present throughout the formation, although their distribution appears to be facies-dependent. Bioturbation becomes more prominent after the transition from siliciclastic to carbonate layers, and is most pronounced in carbonate beds containing Thalassinoides (inchnofabric indices of 3 to 4). The March Point Formation records transgression and highstand during Series 3 Cambrian time, and allows for the study of the complex relationship between the preservation and environmental distribution of soft-bodied fossils and bioturbation.