The ultimate goal of all techniques involving spectroradiometry is to provide accurate qualitative or quantitative estimates of sediment composition. Whereas many studies have already shown that different marine sediments have distinctive spectral features, most of these previous studies focus primarily on the visible and "very" near-infrared region of the electromagnetic spectrum. For example, Balsam et al. (1999) evaluated the use of visible light (400-700 nm) spectroscopy, or optical lightness, as a proxy for the carbonate content of marine sediments in five piston cores from Hole 997A. They concluded that measures of optical lightness are reasonable proxies for relative changes in carbonate content over short spans of geologic time, but for longer periods of time, the relationship is not well defined. They also warn that optical lightness is strongly affected by the composition of the noncarbonate fraction, such as clay. Mix et al. (1992, 1995) analyzed reflectance spectra in the visible and near-infrared bands (455-945 nm). Their goal was to estimate biogenic calcite, biogenic opal, and nonbiogenic contents from cores recovered during ODP Leg 138. Their estimates were best for biogenic calcite, but opal and nonbiogenic material were not always distinguished reliably. Balsam and Deaton (1996) used spectra from the range of 250-850 nm to estimate concentrations of carbonate, opal, and organic contents in Atlantic and Pacific marine cores. They found that the character of downcore changes in mineralogy was well determined, but systematic offsets were sometimes evident for individual mineral concentrations.
Our LAS technique measures spectra over the entire visible and near-infrared region of the electromagnetic spectrum (350-2500 nm). This study demonstrates that the additional spectral information found in the near-infrared region could greatly improve identification of minerals with paleoclimatic interest.