VOLCANIC LOADING OF METALS AND NUTRIENTS INTO THE CRETACEOUS BOREAL SEA – NOT ALL LIPS ARE KILLERS

Cretaceous sediments of Arctic Canada were deposited at near present day latitudes and provide insight into the impacts that the High Arctic Large Igneous Province (HALIP) and arc volcanism along western North America had within the Cretaceous Boreal marine environment. Here we examine Upper Cretaceous sediments from the Smoking Hills, on the northern mainland coast of Arctic Canada, in the Northwest Territories. These sediments include the anomalous bituminous mudstone of the Smoking Hills Formation occurs, that is characterised by a prominent negative carbon isotope excursion. Likely deposited during OEA3, the Smoking Hills Formation is a pyritiferous mudstone enriched in organic matter (mean total organic carbon content of 5.2 wt. %) and trace metals (maximum values expressed as multiples of average shale composition are: Cd 650x, Zn 12x, As 14x, Cu 3.4x, Pb 2.2x, Ni 2.0x, Co 1.7x, Cr 1.3x). A strong correlation between total trace metal content and heulandite (a zeolite mineral formed as an alteration product of volcanic glass) suggest a relationship between metal loading and volcanism. While geochemical indicators indicate euxinic bottom waters formed at this time, abundant organic matter and marine fauna indicate a highly productive oxic surface waters in the Cretaceous Boreal realm. We suggest that volcanic emissions at this time provided nutrient loading to the boreal sea boosting primary productivity, which led to bottom-water anoxia and black shale deposition.