G02_P10

Age offsets between marine-derived lipid biomarkers, TOC, and foraminifera during cross shelf-slope lateral transport revealed by compound-specific radiocarbon dating

UCHIDA M¹,   Eglinton T², Coppola L³, Gustafsson Ö⁴, Mollenhauer G⁵, Hayes J^6,8, Ahagon N⁷, Harada N⁷

¹Earth System Division, National Institute For Environmental Studies, Tsukuba, Japan, ²Geological Institute, ETH, Zurich, Switzerland, ³Villefranche-sur-mer, Alpes Maritimes, France, ⁴Institute of Applied Environmental Research, Stockholm University, Stockholm, Sweden, ⁵Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, ⁶National Ocean Sciences Accelerator Mass Spectrometry facility, Woods Hole Oceanographic Institution, Woods Hole, U.S.A., ⁷Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan, ⁸Deceased 3 February 2017, ,

Compound-specific radiocarbon analysis was performed on bulk sediments and different grain-size fractions (>250μm, 150-250μm, 63-150μm,38-63μm, <38μm) of shelf-slope surface sediments (0-2cm, outer shelf of 150m water depth and upper slope of 600m water depth) from Washington Margin to examine their relationships between hydrodynamic sorting of sediments and timescales and preservation of organic carbon. Here we obtained datasets of radiocarbon ages of alkenone, low molecular weight fatty acids (LMW-FAs, C₁₄, C₁₆, and C₁₈), high molecular weight fatty acids (HMW-FAs, C₂₄, C₂₆, and C₂₈), total organic carbon and planktic foraminifera. These results were also discussed with previous reported lateral transport times of organic carbon (Bao et al., 2019). Age offsets between planktonic foraminifera, LMW-FAs, and alkenone in bulk phase sediments were significantly large in shelf compared with slope. On the other hand, age offsets between size fractions were not likely observed between LMW-FAs and alkenone except for large fractions(>250μm). Ages of LMW-FAs for both shelf and slope were younger than those of alkenone in all fractions including bulk-phase sediments. Moreover, we obtained radiocarbon ages of marine-derived compounds (alkenone, LMW-FAs), plant wax-derived compounds(HMW-FAs), planktic foraminifera, and total organic carbon from the last deglaciation- Holocene covered-marginal sediments from western North Pacific (1366m water depth, N41°) and Okhotsk Sea (1225m water depth, N44°). We discuss with palaeoceanographic interpretation on sedimentary records such as alkenone temperatures and ventilation.