Many of the most exciting problems in paleoclimate need to be addressed with high-resolution records: (1) climate fluctuations driven by Milankovitch orbital changes; (2) refinement of the biostratigraphic and magnetostratigraphic timescale using Milankovitch cycles; (3) asymmetries in warming vs. cooling half cycles; (4) correlations among glacial, oxygen isotope, and sea level fluctuations; and (5) correlations between Northern Hemisphere and Southern Hemisphere climate changes. Some marine sedimentary sequences contain potentially detailed records of these variations, but the thousands of needed measurements are too time consuming.
An alternative approach is that of calibrated climate proxies. Some measurement types (e.g., downhole logs and Ocean Drilling Program [ODP] whole-core physical properties) are rapid enough to permit development of high-resolution records. If variations within these records can be associated with climate change via calibration to a relatively small suite of ground-truth data, then these data can provide a high-resolution climate proxy. Examples of these variations are the demonstration of Milankovitch cycles in ODP downhole logs (Jarrard et al., 1988; Jarrard and Arthur, 1989; deMenocal et al., 1992), ODP multisensor track density and magnetic susceptibility records (deMenocal et al., 1991; Shackleton et al., 1995; Shackleton and Crowhurst, 1997), and ODP digital color records (Niitsuma, 1991).
In this paper, we explore the possibility of using light absorption spectroscopy (LAS) as a way to obtain high-resolution, semiquantitative mineralogical data from marine cores. The first section of this paper describes several feasibility studies that have been undertaken to establish LAS as a useful mineralogy tool. The second part of this paper outlines a more sophisticated calibration method, which was used to determine mineralogy during ODP Leg 199. A detailed interpretation of the Leg 199 LAS data will be included in the Leg 199 Scientific Results volume.