The presented data originates from the 1306cm long gravity core MSM45-19-2 (58°45.68 N, 61°56.25 W, 202m water depth) taken during R/V Maria S. Merian cruise MSM45 in August 2015 at 202 m water depth on the northern Labrador Shelf, northeast Canada, northwest Atlantic. Here, we present a high-resolution and well-dated sediment record from the northern Labrador Shelf that provides new evidence of the freshwater signature and the mechanisms involved in the Hudson Bay Ice Saddle collapse. Elemental composition and color reflectance data reveal sediment dispersal characteristic of the subglacial drainage of LAO. The light reflectance was measured in 1-cm intervals on the foil-covered, air-bubble-free, core surface with a hand-held Konica Minolta CM 600d spectrophotometer on board the research vessel. The spectrum of the reflected light was detected by a multi-segment light sensor at a 20 nm pitch between wavelengths of 400–700 nm. The a(D65) value reflects the ratio of magenta (700 nm) and green (500 nm).The bulk sediment elemental composition was analyzed at Kiel University, using an Avaatech XRF core scanner. The archive half of the core was carefully scraped to create a smooth surface before covering it with a 4-μm-thin SPEXCertiPrepUltralene foil to avoid contamination (Richter et al., 2006). Each section was successively scanned with voltages of 10 kV (10 s, 750 μA, no filter), 30 kV (20 s, 500 μA, Pd-Thin filter), and 50 kV (40 s, 1750 μA, Cu filter) to measure the full suite of elements between Al and Ba in 1-cm resolution. Instrumental variance was monitored by measuring a set of standards (SARM4, JGa-1, JR-1, KGa-1) prior to each section and at the end of daily scanning.Sedimentological changes associated with the LAO drainage event are determined by characteristic peaks in both redness of bulk sediment (color reflectance aD65 values) and relative content of detrital carbonate inferred from elemental Ca/Sr ratios measured by X-ray fluorescence (XRF) core scanning. The most pronounced peak in Ca/Sr occurs between 1073 and 1068 cm, supported by an increase in color reflectance redness.The most significant freshening of subsurface waters is centered at 8.5 ka BP, with apparently two meltwater pulses associated with two cold spells between 8.6 and 8.5 ka BP (Fig. 4d, e). This interval is also characterized by increased levels of red sediment color).The first and less severe of the two freshwater pulses, at about 8.58 ka BP in the δ18Ow-ivc record, correlates with the highest peaks in red sediment color (a*D65) and detrital carbonate (Ca/Sr). Although Jennings et al. (2015) associate the red bed with the opening of the Tyrell Sea, we interpret the first freshening and input of red sediment and detrital carbonate to represent the initial phase of the subglacial LAO outburst flood.
