Abstract
Pedogenic carbonate is widespread at mid latitudes where combined warm
and dry conditions favor soil carbonate growth from spring to fall. The
mechanisms and tempo of pedogenic carbonate formation are more ambiguous
in the tropics, where longer periods of soil water saturation and higher
soil respiration enhance calcite dissolution. This paper provides bulk
and clumped isotope values from Quaternary and Miocene pedogenic
carbonates in the tropical monsoonal domain of Myanmar where annual
rainfall reaches up to 1700 mm. We show that carbonate growth in Myanmar
is delayed to the coldest months of the year by sustained rainfall from
mid spring to late fall. We propose that high soil moisture year-round
in the tropical domain makes carbonate growth more episodic than in
temperate ecosystems, and particularly sensitive to the seasonal
distribution of rainfall. This sensitivity is also enhanced by high
winter temperatures, allowing carbonate growth to occur outside the
warmest months of the year. This high sensitivity is expected to be more
prominent in the geological record during times with higher temperatures
and greater expansion of the tropical realm. The winter bias in TD47
values found in Burmese soils, unique for pedogenic carbonates,
constitute a potential signature for past tropical monsoonal (warm
summer-wet) climates in paleosols, and are also found in our Miocene
samples.