Spectral data from IODP Sites U1456 and U1457, Arabian Sea

Diffuse reflectance spectroscopy (DRS) data are routinely collected by IODP. DRS data were collected at the IODP Gulf Coast Repository (GCR) in College Station, Texas (USA) using a hand-held Minolta CM-2002 Spectrophotometer. Those data spanning 5.5–8.5 Ma at Site U1456 were already published by Clift et al. (2019a). Sediment reflectance spectra between 390–700 nm wavelength range were measured every 2 cm along each core because this range covers most iron oxyhydroxides for mineral reflectance (Deaton and Balsam, 1991). For each measurement the percent of light intensity reflected from the sample surface was obtained at a 10 nm interval. During data collection the spectrophotometer was fully in contact with the core surface at the time of measurement. Interference from outside light was avoided in order to increase the accuracy of the reflectance data. The archive half was carefully scraped and rewrapped with Glad Cling plastic wrap during the scanning. This wrap is commonly used for shore-based scanning work on IODP/ODP cores (Balsam et al., 1997). Measurements of the sediment spectral reflectance are not distorted as a result and raw results can be considered to be reliable. Evaporation during storage resulted in the core surface being drier compared to after initial splitting.漫反射光谱法（Diffuse reflectance spectroscopy, DRS）数据是国际大洋发现计划（International Ocean Discovery Program, IODP）的常规采集数据集。本次研究的DRS数据采集于美国得克萨斯州大学城的国际大洋发现计划墨西哥湾海岸馆藏库（Gulf Coast Repository, GCR），采用手持式美能达CM-2002型分光光度计完成。U1456站位中跨度为5.5–8.5 Ma的相关数据已由Clift等人（2019a）公开发表。沿每根岩芯以每2 cm的间距开展测量，采集390–700 nm波长范围内的沉积物反射光谱；该波段覆盖了绝大多数用于矿物反射表征的羟基氧化铁（Deaton与Balsam, 1991）。每次测量均以10 nm的步长获取样品表面的反射光强百分比。测量过程中，分光光度计始终与岩芯表面完全贴合，同时规避了外界光线的干扰，以提升反射光谱数据的准确性。扫描期间，工作人员对存档半芯进行了细致刮平，并使用Glad保鲜保鲜膜进行包裹；该保鲜膜是国际大洋发现计划/大洋钻探计划（Ocean Drilling Program, ODP）岩芯岸基扫描工作中的常用耗材（Balsam等人, 1997）。该操作未对沉积物光谱反射率的测量结果造成畸变，原始测量数据可被视为可靠结果。但在储存过程中，岩芯表面因蒸发作用出现失水干燥，其湿度较初始岩芯拆分后有所降低。