Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits

S Hage,R.G Hilton,C.A Mcghee,C.D Stacey,D.R Parsons,V.V Galy,D.G Lintern,P.J Talling,J.E Hunt,M.J.B Cartigny,D.R Gröcke,E.J Sumner,M.A Clare,S Acikalin

doi:10.1130/g47320.1

Abstract

Abstract Burial of terrestrial biospheric particulate organic carbon in marine sediments removes CO2 from the atmosphere, regulating climate over geologic time scales. Rivers deliver terrestrial organic carbon to the sea, while turbidity currents transport river sediment further offshore. Previous studies have suggested that most organic carbon resides in muddy marine sediment. However, turbidity currents can carry a significant component of coarser sediment, which is commonly assumed to be organic carbon poor. Here, using data from a Canadian fjord, we show that young woody debris can be rapidly buried in sandy layers of turbidity current deposits (turbidites). These layers have organic carbon contents 10× higher than the overlying mud layer, and overall, woody debris makes up &gt;70% of the organic carbon preserved in the deposits. Burial of woody debris in sands overlain by mud caps reduces their exposure to oxygen, increasing organic carbon burial efficiency. Sandy turbidity current channels are common in fjords and the deep sea; hence we suggest that previous global organic carbon burial budgets may have been underestimated.

Highlights

It is important to constrain the burial of terrestrial biospheric particulate organic carbon (POC) in marine sediments because it is the second-largest sink of atmospheric CO2 after weathering of silicate minerals (Gaillardet et al, 1999), and thereby contributes to long-term regulation of climate (Berner, 1982)
Woody debris associated with sands in submarine fans is increasingly being recognized as a major terrestrial POC pool (Leithold et al, 2016; Lee et al, 2019)
Here we assess the distribution of three POC types buried in turbidites that resulted from a turbidity current that was directly measured in Bute Inlet, British Columbia, Canada

Summary

Introduction

It is important to constrain the burial of terrestrial biospheric particulate organic carbon (POC) in marine sediments because it is the second-largest sink of atmospheric CO2 after weathering of silicate minerals (Gaillardet et al, 1999), and thereby contributes to long-term regulation of climate (Berner, 1982). The quantitative budget, age, and composition of POC within sandy turbidity-current deposits compared to that in fine sediment has not been considered.

Results

Conclusion