Deciphering Color Reflectance Data of a 520‐kyr Sediment Core From the Southern Ocean: Method Application and Paleoenvironmental Implications

• Published in: Geochemistry, geophysics, geosystems : G3 Vol. 20; no. 6; pp. 2808 - 2826
• Main Authors: Wu, Li, Wang, Rujian, Krijgsman, Wout, Chen, Zhihua, Xiao, Wenshen, Ge, Shulan, Wu, Jiawang
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01.06.2019
• Subjects: Algorithms; Carbon; Chlorite; Clay; Clay minerals; color reflectance; Colour; Components; Cores; Data; Factor analysis; Fe minerals; Fluorescence; Goethite; Haematite; Hydroxides; Interglacial periods; Iron; Manganese; marine sediment; Mineral composition; Mn peaks; Moisture content; Oceans; Opal; Organic carbon; Oxides; Ratios; Reflectance; Sediment; Sediments; Southern Ocean; Total organic carbon; Variance analysis; Ventilation; Water content; Water currents; X-ray fluorescence; Southern Ocean
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2019GC008212

Sediment color reflectance contains important information on paleoenvironmental changes. Such data are routinely measured on sediment cores from the Southern Ocean. Their usefulness, however, is undervalued. Here for the first time, color reflectance of an ~520‐kyr sediment core retrieved off Prydz Bay (East Antarctica) was intensively investigated to correlate sediment color changes to changes in sediment compositions. Total carbon, total organic carbon, X‐ray fluorescence‐derived Fe/Ti and Br/Ti ratios, water content and mineral composition of sediment from this core, and color reflectance of another two sediment cores retrieved nearby were analyzed in this study. The raw reflectance data were transformed into their first‐order derivatives and subjected to factor analysis algorithms. A four‐factor model was selected to unmix the data set, explaining >80% of the total data variance. Its robustness is supported by similar factor analysis results from the other two cores. The four factors represent (from Factors 1–4) pulses of sedimentary Mn enrichment and Fe3+/Fe2+ changes in clay minerals, relative content changes of colorless components, hematite and goethite, and water, respectively. Scores of Factor 1 show high spikes at glacial terminations, recording enhanced deglacial ventilation in the abyssal Southern Ocean. Scores of Factor 2 mainly reflect biogenic components and chlorite but are further complicated by refractory terrigenous organic carbon and Mn‐oxides/‐hydroxides. Higher Scores of Factor 3 occur mainly at peak interglacial intervals, associated with enhanced transport of sediment of Antarctic origin by oceanic currents. Water content (Factor 4) in the core sediment was significantly influenced by opal content and sediment grain size compositions. Key Points Factor analyses are used to decipher sediment color reflectance data from the Southern Ocean for the first time Four factors control sediment color changes, indicative of useful core parameters and paleoenvironmental proxies Information on abyssal ocean ventilation, relative abundance of hematite and goethite, and water content were obtained from the color data