24-23 New evidence for a Storegga Slide Tsunami deposit in Northeast Greenland

Session: Lake Sedimentary Records of Past Climate and Environment (Posters)

Presenting Author:

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Abstract:

The largest known submarine landslide in the Holocene, the Storegga Slide, occurred off the coast of Norway approximately 8,200 cal yr BP. The wide-reaching extent of the resulting tsunami is important to understand as a stratigraphic marker, for the erosion and redeposition of marine sediments around this already climatically important time frame, and for the impact on human populations. Tsunami deposits have been found throughout Norway, England, and Scotland; deposits across the Atlantic in Greenland are few, with only one known occurrence in coastal East Greenland, even though modeling studies suggest there could have been a 3 m high wave in that area. We present a new sediment record from Germania Land, Northeast Greenland, that we hypothesize contains reworked marine sediment that was deposited from the Storegga Tsunami. Our sediment core is from an isolation basin (informally named “G6”; 76.794ºN, -18.419ºW) at 26 m above sea level with a 4.7 m depocenter. The sediment core is 45 cm long and contains two units. Unit 1 ranges from 53 cm to 10 cm and is comprised of coarse sand with disturbed organic-rich mats of marine brown algae with small cobbles. Unit 2 ranges from 10 cm to 8 cm and is comprised of silty clay with a few lacustrine macrofossils. Radiocarbon ages from within Unit 1 on a terrestrial macrofossil (Salix sp.) are 8,000 ± 180 cal yr BP and from marine algae are 8,010 ± 190 cal yr BP (with a ΔR -46 ± 57). We will present results from two more radiocarbon samples on marine algae to increase our confidence in the timing of this deposit. A new relative sea level record places the depocenter of G6 ~12 m below sea level at the time of the tsunami. Another isolation basin that was 7 m higher than sea level at the time of the tsunami contains undisturbed lacustrine sediments from 8,600 cal yr BP onward, which means the runup from this tsunami would be less than 7 m asl. This may be a useful marker bed in sediment cores or uplifted marine sediments along East Greenland and shows how far (1,700 km!) the impact of this slide can be found.

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