Oxygen isotopes reveal glacial-interglacial changes in the timing of
pedogenic carbonate growth from the Chinese Loess Plateau
Abstract
Pedogenic carbonates document a wealth of environmental information, but
their seasonal variations may obscure long-term trends. Here we report
evidence of changing seasonality of pedogenic carbonate growth from the
Chinese Loess Plateau during the Quaternary glacial cycles, using the
d18O of pedogenic carbonates
(d18Oc). The glacial and interglacial
d18Oc show negative and positive
correlations with proxy-inferred rainfall amount, respectively. We
explain this pattern using modern observations and modeling results,
which show opposite correlations between
d18Oc and rainfall amount in growing
versus non-growing seasons. In glacial episodes under weak monsoon,
pedogenic carbonate growth occurred within the growing season,
inheriting a negative d18Oc-rainfall
correlation. Conversely, pedogenic carbonate growth likely extended into
the non-growing season during interglacials due to intensified monsoonal
rainfall, incorporating a positive
d18Oc-rainfall correlation. Our work
links seasonal fluctuations of pedogenic carbonates with their long-term
records, shedding new light on interpreting this paleoarchive.