OBLIQUITY AND ECCENTRICITY SIGNALS FOUND IN A META-ANALYSIS OF SOIL CHRONOSEQUENCES

Quaternary climate periodically fluctuated in concert with orbital variation in incoming solar radiation. Evidence of orbitally-driven climate change has been found in loess deposits, marine sediments, and ice cores. While, Quaternary climate variability is a significant driver in sediment production and deposition and soil formation, a key knowledge gap exists in our understanding of critical zone-climate change feedbacks due to the lack of evidence of orbitally-driven climate change in soil systems. To fill this gap, a meta-analysis of soil chronosequences was performed; we hypothesized that soil ages represent a proxy for orbitally-driven climate change. Using the soil chronosequences, we calculated a soil age time series, which represented a record of Quaternary soil preservation. We found significant periodicities in the soil age time series at 41 kyr and 98 kyr, aligning with obliquity and eccentricity orbital cycles. By comparing soil ages to paleoclimate proxies, we found that soils dated predominantly to warm interglacial periods with relatively low rates of climate change following rapid glacial-to-interglacial transitions. Our results suggest that orbitally-driven climate change drove punctuated periods of sediment production and deposition, with this sediment serving as the parent material for soil formation, tying soil ages to orbital climate cycles. Further, soil formation may feed back into Quaternary climate variability through consumption of carbon dioxide in soil formation processes. These results provide a key insight into Quaternary critical zone evolution and paleo-environmental change.