Provenance of sediment in the Labrador Current: a record of hinterland glaciation over the past 125 ka

Abstract

The Labrador Current flows southward along the continental margin off eastern Canada and is the principal source of sediment to the outer continental margin areas where ice sheets did not cross the continental shelf. We present multi-proxy mineralogical and geochemical records based principally on X-ray diffraction and X-ray fluorescence for core 2011031-059 from northern Flemish Cap to determine changes in supply and hence to reconstruct provenance evolution during the last glacial cycle. The calcite to dolomite ratios in Heinrich layers ranged from 2 to 4, suggesting carbonate layers derived from Hudson Strait as early as Marine Isotope Stage (MIS) 5a-d. Mineral abundance shows three time-dependent predominant sediment sources other than in Heinrich layers: (i) Baffin Bay shelves and adjacent land in MIS 5 and 1, with high Ca, Sr, kaolinite and feldspars and low clay minerals and calcite/dolomite ratios; (ii) Labrador in MIS 3, with low clays and grey color; and (iii) north-east Newfoundland Shelf in MIS 2 and 4, with higher concentrations of clay minerals, red sandstones and transition elements. These results allow a reconstruction of principal ice streams supplying the north-west Atlantic over the last full glacial cycle.

Alkenone paleothermometry in the North Atlantic: A review and synthesis of surface sediment data and calibrations

“…Mao et al . [] speculate that alkenone‐based SST estimates far exceeding possible surface ocean temperatures in the Labrador Sea are the result of glacial erosion on the continental shelf of Cretaceous and Paleogene highstand limestone and chalks, which contain abundant coccolithophores, and potentially alkenones.…”

The influence of meltwater on the Labrador Current in Heinrich event 1 and the Younger Dryas

“…The proxy of SS is also influenced by the grain size distribution in the source area of the sediment and the silt component derived from ice-rafting (McCave and Mulder et al, 2013). The effect of variations in source area is minimized in this study by decarbonation, as the siliciclastic and crystalline basement sources of glacial sediment do not appear to change significantly between Heinrich layers and other late Pleistoceneeearly Holocene intervals (Piper and de Wolfe, 2003;Mao et al, 2014), being largely derived from the Labrador margin (Roger et al, 2013). The role of IRD is assessed by comparing the proxy of SS with or without a Hass (2002) correction.…”

The Holocene Labrador Current: Changing linkages to atmospheric and oceanographic forcing factors

“…Some sediments were also transported in dilute suspension in the LC. The proportions of platy clay‐sized minerals relative to more equant minerals vary somewhat through time [ Mao et al , ], but the S̅S̅ determined from both bulk and decarbonated sediment (Figure a) deposited by the LC in Flemish Pass [ Li and Piper , ] covers a range of petrological types. The trends shown by the bulk and decarbonated S̅S̅ curves in the records of Li and Piper [] show almost identical downcore patterns over a wide range of detrital carbonate contents (i.e., CaCO 3 (%)) (Figure a), representing the full range of variation in sediment sources and ratio of rock flour to clay minerals.…”