Dynamics of Pedogenic Carbonate Growth in the Tropical Domain of Myanmar
Dynamics of Pedogenic Carbonate Growth in the Tropical Domain of Myanmar
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DOI：
10.1029/2021gc009929
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发表时间：
2022-07-01
影响因子：
3.5
通讯作者：
Aung, Day Wa
中科院分区：
文献类型：
--
作者：
Licht, A.;Kelson, J.;Aung, Day Wa
成壤碳酸盐在中纬度地区广泛分布，温暖干燥的条件有利于土壤碳酸盐从春季到秋季的生长。成土碳酸盐形成的机制和时间在热带地区更为模糊，在那里，长时间的土壤水分饱和和高土壤呼吸增强方解石溶解。本文提供了缅甸热带地区第四纪和中新世成壤碳酸盐的稳定碳、氧和聚集同位素值，这些地区的特点是温暖的冬季（>18摄氏度），年降雨量高达1,700毫米。我们表明，由于从仲春到晚秋的持续季风降雨，缅甸的碳酸盐生长被推迟到一年中最干燥和最寒冷的月份。第四纪成壤碳酸盐岩同位素变异的范围，可以单独解释的时间变化的碳酸盐岩生长在旱季，从冬季到早春。我们建议，高土壤湿度全年在热带地区缩小碳酸盐的增长，最干燥的月份，使其特别敏感的季节性降雨分布。这种敏感性也是由冬季的高温造成的，使得碳酸盐的生长发生在一年中最温暖的月份之外。在温度较高和热带地区扩张较大的时期，这种高敏感性预计将在地质记录中更为突出。热带成壤碳酸盐岩的成块同位素温度、δ C-13和δ O-18值受降雨季节性和地表温度变化的影响;这种敏感性可用于跟踪过去的热带降雨分布。
Pedogenic carbonate is widespread at mid latitudes where warm and dry conditions favor soil carbonate growth from spring to fall. The mechanisms and timing of pedogenic carbonate formation are more ambiguous in the tropical domain, where long periods of soil water saturation and high soil respiration enhance calcite dissolution. This paper provides stable carbon, oxygen and clumped isotope values from Quaternary and Miocene pedogenic carbonates in the tropical domain of Myanmar, in areas characterized by warm (>18 degrees C) winters and annual rainfall up to 1,700 mm. We show that carbonate growth in Myanmar is delayed to the driest and coldest months of the year by sustained monsoonal rainfall from mid spring to late fall. The range of isotopic variability in Quaternary pedogenic carbonates can be solely explained by temporal changes of carbonate growth within the dry season, from winter to early spring. We propose that high soil moisture year-round in the tropical domain narrows carbonate growth to the driest months and makes it particularly sensitive to the seasonal distribution of rainfall. This sensitivity is also enabled 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. Clumped isotope temperatures, delta C-13 and delta O-18 values of tropical pedogenic carbonates are impacted by changes of both rainfall seasonality and surface temperatures; this sensitivity can potentially be used to track past tropical rainfall distribution.