EGU2020-824
https://doi.org/10.5194/egusphere-egu2020-824
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

230Th-excess inventory and distribution in a southern Mendeleev Ridge core (Arctic Ocean): linkage with late Quaternary sedimentological and paleogeographical changes

Tengfei Song1, Claude Hillaire-Marcel1, and Yanguang Liu2
Tengfei Song et al.
  • 1Université du Québec à Montréal, GEOTOP, Doctorat en sciences de la Terre et de l'atmosphère, Montreal, Canada
  • 2First Institute of Oceanography, MNR, Qingdao, China

In addition to 14C-data, sedimentary excesses in 230Th  (230Thxs) in central Arctic Ocean cored sequences yielded critical time constrains and sedimentation rates estimates, at least, at sites characterized by very low sedimentation rates (<< 1cm/ka). Closer to the Russian margin, where higher accumulation rates are recorded based on 14C-ages, the setting of a reliable stratigraphy based on 230Thxs reveals more challenging, as illustrated here, based on the analysis of  a gravity core raised from the southern Mendeleev Ridge (core ARC7-E25; -179.4°E, 79.0°N; 1200 m water depth; 320 cm long). Subsamples were collected at a 4 to 8 cm interval. Measurements included: AMS 14C in foraminifera, grain size, bulk Xray mineralogy, clay mineralogy, geochemistry (Corg, Cinorg,13Corg, 238U, 234U, 230Th, 226Ra, 210Pb). Data indicate that some sediment were lost at core top. Nevertheless, 14C and 230Thxs  data allow estimating a mean sedimentation rate of about 6 to 7 mm/ka during the last two climatic cycles. A comparison of the 230Thxs inventory and distribution pattern with those from other cores allows identifying important parameters involved in the cycling of the water column-produced 230Th in this basin and its sporadic sedimentary accumulation, in particular linkages with sea-ice production over shelves, thus sea-levels, sea-ice rafting routes, grain-size and mineralogy, potential winnowing of fine fractions, role of brines and relative duration of intervals with reduced or nil sedimentation preceding 230Thxs-accumulation intervals.

How to cite: Song, T., Hillaire-Marcel, C., and Liu, Y.: 230Th-excess inventory and distribution in a southern Mendeleev Ridge core (Arctic Ocean): linkage with late Quaternary sedimentological and paleogeographical changes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-824, https://doi.org/10.5194/egusphere-egu2020-824, 2019