Paleogene paleosols and changes in pedogenesis during the initial Eocene thermal maximum: Big Bend National Park, Texas, USA
Paleogene paleosols and changes in pedogenesis during the initial Eocene thermal maximum: Big Bend National Park, Texas, USA
复制标题
DOI：
10.1130/b25987.1
复制
发表时间：
2008-11
影响因子：
4.9
通讯作者：
Paul White;J. A. Schiebout
中科院分区：
文献类型：
--
作者：
Paul White;J. A. Schiebout
本文通过比较德克萨斯州西部始新世热峰期之前和期间形成的古土壤，检验了大陆化学风化在始新世热峰期（IETM）初期增加的假设。用化学蚀变指数（CIA）研究了硅酸盐矿物的风化作用。在IETM之前产生的古土壤的CIA值范围为62至72，IETM期间的CIA值范围为67至82。前初始始新世热最大古土壤的CIA值表明中等风化条件，和CIA值在事件期间表示中度至极端风化条件。古土壤的粘土矿物学以蒙皂石为主，只有在IETM期间形成的古土壤中才有变化。有一个显着增加的高岭石的量在一个古土壤层，这是与碳漂移。此外，有一个增加的易位的粘土和铁，并增加在最初的始新世热最大古土壤中的方解石和斜长石的淋溶。在始新世初始热峰期之前和期间形成的土壤之间的差异表明，在这一古老的全球变暖事件期间，化学风化确实增加了。负责增加风化的机制被解释为增加在土壤中的湿度和碳酸的增加，由于在最初的始新世热最大值的CO2水平升高引起的水解反应。在最初的始新世热最大值期间，化学风化的增加是显着的，因为它可能起到了减少大气CO2的负反馈作用。
This paper tests the hypothesis that continental chemical weathering increased during the initial Eocene thermal maximum (IETM) by comparing paleosols that formed before and during the event in western Texas. The chemical index of alteration (CIA) was used to investigate the weathering of silicate minerals. Paleosols generated before the IETM have CIA values ranging from 62 to 72, and CIA values during the IETM range from 67 to 82. The CIA values for pre–initial Eocene thermal maximum paleosols indicate moderate weathering conditions, and CIA values during the event indicate moderate to extreme weathering conditions. The clay mineralogy of the paleosols is dominated by smectite, and it is only within paleosols that formed during the IETM that there is a change. There is a notable increase in the amount of kaolinite in one paleosol horizon that is associated with the carbon excursion. In addition, there is an increase in the translocation of clays and iron, and an increase in the leaching of calcite and plagioclase in initial Eocene thermal maximum paleosols. The differences between soils that formed before and during the initial Eocene thermal maximum indicate that chemical weathering did increase during this ancient global warming event. The mechanism responsible for increased weathering is interpreted to be an increase in hydrolysis reactions caused by an increase in humidity and an increase of carbonic acid in the soil due to elevated CO2 levels during the initial Eocene thermal maximum. Documentation of an increase in chemical weathering during the initial Eocene thermal maximum is significant because it may have served as a negative feedback to reduce atmospheric CO2.