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.