USING INSIGHTS FROM PALEOGENE WEATHERING AND PALEOSOL FORMATION TO SOLVE QUATERNARY PROBLEMS

When well preserved, paleosols offer a wide range of paleoenvironmental and paleoclimate information. Major and trace elemental and isotopic data may be used to examine temporal environmental variation and to reconstruct chemical and physical weathering at the process scale. Increasing recognition of paleosols in continental successions has opened up new avenues of paleoclimatic research, often with much better spatial resolution than in marine successions, including paleohydrological insights. Furthermore, geochemical climofunctions derived from modern soils have been applied to Mesozoic and Cenozoic paleosols in places where independent paleoclimatic proxies such as plant fossils exist, confirming the reconstructed paleoclimatic and paleoenvironmental conditions inferred from the climofunctions. In this sense, the present is the key to past. At the same time, the success of these proxies in predicting environmental and process-level information for older paleosols suggests that they are also useful for reconstructing more recent weathering and soil formation in Quaternary sequences with limited or no field exposure. Thus, the past may also be the key to the (nearly) present.

The upper kilometer of the Hawaiian Scientific Drilling Program core consists of lavas that were emplaced subaerially, burying paleosols. These paleosols were preserved with minimal alteration and are used to construct a ~330 kyr Quaternary climate record. Within the temporal resolution of this record, there appears to be a ~100 kyr climate oscillation between cool-dry and warm-wet conditions, indicating that tropical regions such as Hawaii have responded to the same global climate forcings as higher latitude areas during at least the past three glacial-interglacial cycles. It is also suggested that Hawaiian climate may have become progressively warmer and wetter over the same period.