Bryozoan-rich layers in surficial Labrador Slope sediments, eastern Canadian Arctic

Abstract

Layers rich in remains of a shallow-water bryozoan species, Idmidronea atlantica, have been found in Quaternary sediments in a piston core taken from 1085 m water depth in the Labrador Sea (59.700270°N, 60.238370°W), tens of kilometres from the nearest possible source. These layers occur anomalously in pelagic–hemipelagic muds with abundant planktic and deep-water benthic foraminifera, and are thus not in sediments attributable to mud turbidite or debris flows. The bryozoan remains appear to be most common in intervals just below Heinrich events H1 and H2 (~14 500 and ~20 600 14C years BP, respectively). Two possible ice-related transport mechanisms are suggested to have been involved in the deposition of the bryozoan fragments. The first method involved the scouring action of loose pack ice and (or) bergs dislodging and mobilizing attached bryozoans in shallow water, where they could be subsequently entrained in currents and transported to deeper water. The second method may have occurred when attached colonies of these animals were frozen in place as winter ice formed in shallow water, to be carried out to deeper conditions while still encased in loose floes the subsequent spring–summer.