Preservation and characteristics of Organic Carbon in submarine lobe deposits of the Battfjellet Formation, Svalbard

Abstract

Organic Carbon (OC) burial in marine sediments is the second biggest sink of atmospheric CO2 on a geological timescale. Little quantitative research has been done on OC preservation in turbidite systems and OC preservation is poorly constrained, despite turbidites being reported as an important OC sink. This thesis investigates the extent to which turbidites are substantial OC sinks using quantitative data. This is achieved by analyzing the distribution of Particulate Organic Carbon (POC) size, Total Organic Carbon (TOC), and OC source (δ13C) of 66 samples from a sandy turbidite lobe of the Battfjellet Formation, deposited during the Eocene on Svalbard. Results are compared to pre- existing logs and mineral grain size distributions. Results show that POC size decreases in the lobe from 2.81 φ (Krumbein phi scale, 0.17 mm) in the most proximal sub-environment to 3.07 φ (0.14 mm) in the distal sub-environment due to hydrodynamic sorting. TOC values increase from an average 0.19wt% at the most proximal location to 0.38wt% at the most distal location, again as a result of hydrodynamic sorting. Stable carbon isotope analysis reveals that the proximal sub-environment has a largely terrestrial input with an average δ13C value of -20.9‰, with an increasing marine input in the distal fringe sub-environment at an average δ13C value of -23.7‰. Average TOC content is integrated over the volume of the lobe, the total amount preserved in the sandy lobe is at least 2001 kg OC/km2/yr. What sets this turbidite lobe apart from other marine sediments is burial rate, where sedimentation rates in turbidite lobes are several magnitudes larger than in surrounding marine sediments, enabling lobes to much more OC. Mapping OC burial in turbidites is essential to better model a carbon cycle on a geological timescale as well as in current systems. This thesis serves as a first step towards this objective.