Foraminiferal, Sedimentological and Ichnological Analysis of Early Cretaceous Sediments (Scotian Shelf)

Grant D. Wach, Flavia Fiorini, and David Scott
Dalhousie University, Halifax, NS

This study describes the foraminiferal, sedimentological and ichnological analysis on samples collected from the early Cretaceous Lower Logan Canyon Formation cored interval from the Cohasset A-52 corresponding to a sea level lowstand. The Cohasset A-52 well is located on the Scotian Shelf approximately 40 km southwest of Sable Island (Nova Scotia Offshore). Eight cored intervals between 2069 and 2221 m comprising 152 m of interbedded gray-black shale and sandstone with shell fragments have been described and sampled. Forty-one samples have been processed for foraminiferal analysis to supplement earlier analysis of cuttings. The majority of samples results in a rich benthic foraminifera assemblage allowing a quantitative characterization of the >63µm fraction.

The foraminiferal associations recorded from the studied cores are characterized mainly by agglutinated specimens of Trochammina, Haplophragmoides, Ammobaculites and Verneulinoides. The foraminiferal associations and abundances from the examined samples are comparable with modern assemblages of salt marshes and estuaries. "Marsh-estuary type" fauna similar to the Cohasset ones has been previously reported from Cretaceous sections in Alberta. The analysis of the occurrence and distribution of "marsh-estuary type" agglutinated foraminifera, together with detailed sedimentological and ichnological analysis of the cores has provided paleoenvironmental characterization of marginal marine and paralic environments.