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doi:10.2204/iodp.proc.318.201.2014

Introduction

Operations in Expedition 318 Hole U1357A in the Adélie Basin, located on the Antarctic continental shelf off the Wilkes Land margin, led to the recovery of a long core of Holocene diatomaceous ooze–dominated sediment. The aim of this expedition was to develop the first annually resolved time series of Holocene oceanographic and climatic variability (see the “Expedition 318 summary” chapter [Expedition 318 Scientists, 2011]). Reconstruction of coastal environmental change in the Holocene has traditionally been achieved using a combination of biological and physical indicators (e.g., pollen, diatoms, foraminifers, and sediment grain size). In addition to these traditional indicators in Holocene sediments, organic geochemical proxies such as total organic carbon (TOC), C/N, δ¹³C_org, and δ¹⁵N_org have also been used to reconstruct oceanographic processes and to understand the origin of the organic materials in these sediments (Lamb et al., 2006; Jacot Des Combes et al., 2008). Rock-Eval pyrolysis is the most basic organic geochemical analysis of sedimentary organic matter, providing valuable parameters, including S₁, S₂, and S₃ peaks, hydrogen index (HI), oxygen index (OI), and T_max to aid discrimination of the type and maturity of the organic matter. Here, we report several results from organic geochemical analyses of the diatomaceous ooze sampled from the Adélie Basin that are vital for understanding the characteristics of the organic matter and identifying the decadal changes in surface productivity during the late Holocene.

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