Detrital mineralogy and petrology of deep-water continental margin sediments off Newfoundland

Abstract

Seventeen long piston cores have been examined from the continental slope and rise off the Grand Banks and from nearby seamounts. Most cores penetrate Holocene and late Wisconsinan sediment. Four main facies groups are distinguished: A — red terrigenous sediment; B — gray terrigenous sediment (including turbidite sands); C — calcareous (mostly biogenic) sediment; and D — diatomaceous sediment. Facies C and D characterize the Holocene and interstadials; facies A and B were developed during stadials.Three suites of ice-rafted debris are distinguished: (i) a metamorphic-dominated suite, derived either from Greenland and Baffin Island or from local Labrador and Newfoundland ice; (ii) a carbonate-dominated suite, derived from the Arctic Islands; and (iii) a red sandstone – siltstone suite, derived from the Gulf of St. Lawrence and its environs.Three heavy mineral assemblages are recognized: on the Grand Banks slope — pyroxene, opaques, amphiboles, and garnet; in Flemish Pass — opaques, pyroxene, garnet, and tourmaline; and on the western Grand Banks rise — opaques, pyroxene, tourmaline, and garnet.In the biogenic facies C and D, which have slower rates of sedimentation and more ice-rafting corresponding to high stands of sea level, there is little geographic variation in clay mineral assemblage, with montmorillonitic minerals dominant. In the terrigenous facies A and B, which accumulated during glacio-eustatic lower sea-level stands, there is considerable geographic variation, suggesting derivation from local sources on the shelf through wave or glacial erosion.