Foraminiferal distribution and sedimentary facies on the Grand Banks of Newfoundland

Abstract

The southern part of the Grand Banks can be divided into three sedimentary regions. The north western region is dominated by gravel-size material; this is probably a reworked glacial sediment and its limit may indicate the seaward edge of the Quaternary ice sheet. The other regions are both dominated by sand-size pro-glacial material reworked in post-glacial times. The southwestern region includes a large area of finer sediment, which shows the highest density of foraminiferal tests. Dominant lineations indicate the probable influence of the Labrador Current and the Gulf Stream in the distribution of sediments.On the Tail of the Bank, an inverse relationship is commonly present between the density of the benthonic tests and the grain-size of the sediment. Of the 88 species present in the benthonic assemblage, 31 occur in 30% or more of the stations and only 5 occur in more than 90% of the stations. Islandiella islandica (Nørvang) is the most abundant species. The distribution of the living/total ratio in the benthonic Foraminifera is erratic, but particular areas of significantly high or low ratios may be related to different rates of sedimentation. The distribution of the planktonic assemblage, dominated by Globigerina pachyderma (Ehrenberg), is apparently controlled mainly by the movement of the Labrador Current waters. The percentage of planktonic tests in the total foraminiferal population decreases sharply on the shallow plateau, inward from the edge of the Bank.